C2 Atoms, Elements and Compounds - IGCSE Combined Science

Atoms, Elements, and Compounds

Syllabus Overview

This note covers the Cambridge IGCSE Combined Science Syllabus topic C2: Atoms, Elements, and Compounds.

How to Use This Note

  1. Syllabus Checklist: Use the syllabus statements as a checklist to identify areas of confidence and weakness.

  2. Review: Consult the relevant sections in the coursebook (pages 274-300) to review the material for any statements you're not confident with.

  3. Video Tutorials: Utilize online resources such as Fuse School, FreeScienceLessons, and Cognito for additional explanations.

C2.3 Ions and Ionic Bonds

Core Concepts

  1. Ion Formation:

    • Cations: Positive ions formed by the loss of electrons.

    • Anions: Negative ions formed by the gain of electrons.

  2. Ionic Bond Definition: An ionic bond is a strong electrostatic attraction between oppositely charged ions.

  3. Formation of Ionic Bonds:

    • Ionic bonds typically form between elements from Group I and Group VII.

    • Dot-and-cross diagrams are used to illustrate electron transfer.

  4. Properties of Ionic Compounds:

    • (a) High Melting and Boiling Points: Due to strong electrostatic forces.

    • (b) Electrical Conductivity: Good when aqueous or molten (ions can move), poor when solid (ions cannot move).

    • (c) Solubility: Generally soluble in water.

Supplement Concepts

  1. Ionic Bonds Between Metals and Non-metals:

    • Formation of ionic bonds between ions of metallic and non-metallic elements.

    • Dot-and-cross diagrams are used to show electronic configurations.

  2. Giant Lattice Structure:

    • Ionic compounds form giant lattice structures.

    • Regular arrangement of alternating positive and negative ions. Example: Sodium chloride (NaCl).

C2.4 Simple Molecules and Covalent Bonds

Core Concepts

  1. Covalent Bond Definition: A covalent bond is formed when a pair of electrons is shared between two atoms.

    • This sharing leads to noble gas electronic configurations.

  2. Formation of Covalent Bonds:

    • Formation of covalent bonds in simple molecules like H2,,Cl2,,H2O,,CH4,,NH_3,and, andHCl.</p></li><li><p>Dot−and−crossdiagramsareusedtoshowelectronicconfigurations.</p></li></ul></li><li><p><strong>PropertiesofSimpleMolecularCompounds:</strong></p><ul><li><p><strong>(a)LowMeltingandBoilingPoints:</strong>Duetoweakintermolecularforces.</p></li><li><p><strong>(b)PoorElectricalConductivity:</strong>Nomobileionsorelectrons.</p></li></ul></li></ol><h5id="78c48f28−205e−43ff−89aa−9e47b3de74f0"data−toc−id="78c48f28−205e−43ff−89aa−9e47b3de74f0"collapsed="false"seolevelmigrated="true">SupplementConcepts</h5><ol><li><p><strong>FormationofCovalentBonds(Continued):</strong></p><ul><li><p>Formationofcovalentbondsinmoleculeslike.</p></li><li><p>Dot-and-cross diagrams are used to show electronic configurations.</p></li></ul></li><li><p><strong>Properties of Simple Molecular Compounds:</strong></p><ul><li><p><strong>(a) Low Melting and Boiling Points:</strong> Due to weak intermolecular forces.</p></li><li><p><strong>(b) Poor Electrical Conductivity:</strong> No mobile ions or electrons.</p></li></ul></li></ol><h5 id="78c48f28-205e-43ff-89aa-9e47b3de74f0" data-toc-id="78c48f28-205e-43ff-89aa-9e47b3de74f0" collapsed="false" seolevelmigrated="true">Supplement Concepts</h5><ol><li><p><strong>Formation of Covalent Bonds (Continued):</strong></p><ul><li><p>Formation of covalent bonds in molecules likeCH3OH,,C2H4,,O2,,CO2,and, andN2.</p></li><li><p>Dot−and−crossdiagramsareusedtoshowelectronicconfigurations.</p></li></ul></li></ol><h4id="dec9a8ec−e926−42bd−9015−27dc597958dc"data−toc−id="dec9a8ec−e926−42bd−9015−27dc597958dc"collapsed="false"seolevelmigrated="true">Elements,Compounds,andMixtures</h4><ul><li><p><strong>Element:</strong>Consistsofatomsofthesamekind(e.g.,oxygen(O),hydrogen(H),helium(He),carbon(C),potassium(K),sodium(Na)).</p></li><li><p><strong>Compound:</strong>Consistsoftwoormorekindsofatomsinafixedratio(e.g.,tablesalt(NaCl),water(.</p></li><li><p>Dot-and-cross diagrams are used to show electronic configurations.</p></li></ul></li></ol><h4 id="dec9a8ec-e926-42bd-9015-27dc597958dc" data-toc-id="dec9a8ec-e926-42bd-9015-27dc597958dc" collapsed="false" seolevelmigrated="true">Elements, Compounds, and Mixtures</h4><ul><li><p><strong>Element:</strong> Consists of atoms of the same kind (e.g., oxygen (O), hydrogen (H), helium (He), carbon (C), potassium (K), sodium (Na)).</p></li><li><p><strong>Compound:</strong> Consists of two or more kinds of atoms in a fixed ratio (e.g., table salt (NaCl), water (H_2O)).</p></li><li><p><strong>Mixture:</strong>Examplesincludeair,milk,andsaladdressing.</p></li></ul><h4id="b427861a−c17d−411d−8ab0−dce0a45b20ec"data−toc−id="b427861a−c17d−411d−8ab0−dce0a45b20ec"collapsed="false"seolevelmigrated="true">AtomicStructure</h4><ul><li><p><strong>Components:</strong>Protons,neutrons,andelectrons.</p></li><li><p><strong>CarbonAtomExample:</strong>6protons,6neutrons.</p></li><li><p><strong>Location:</strong>Protonsandneutronsinthenucleus;electronsoutsidethenucleus.</p></li></ul><h4id="fa458a4e−4fcf−4456−b924−d133a5c221ff"data−toc−id="fa458a4e−4fcf−4456−b924−d133a5c221ff"collapsed="false"seolevelmigrated="true">SubatomicParticles</h4><tablestyle="min−width:100px"><colgroup><colstyle="min−width:25px"><colstyle="min−width:25px"><colstyle="min−width:25px"><colstyle="min−width:25px"></colgroup><tbody><tr><thcolspan="1"rowspan="1"style="text−align:left;"><p>Particle</p></th><thcolspan="1"rowspan="1"style="text−align:left;"><p>Charge</p></th><thcolspan="1"rowspan="1"style="text−align:left;"><p>RelativeMass</p></th><thcolspan="1"rowspan="1"style="text−align:left;"><p>Location</p></th></tr><tr><tdcolspan="1"rowspan="1"style="text−align:left;"><p>Electron</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>−1</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>)).</p></li><li><p><strong>Mixture:</strong> Examples include air, milk, and salad dressing.</p></li></ul><h4 id="b427861a-c17d-411d-8ab0-dce0a45b20ec" data-toc-id="b427861a-c17d-411d-8ab0-dce0a45b20ec" collapsed="false" seolevelmigrated="true">Atomic Structure</h4><ul><li><p><strong>Components:</strong> Protons, neutrons, and electrons.</p></li><li><p><strong>Carbon Atom Example:</strong> 6 protons, 6 neutrons.</p></li><li><p><strong>Location:</strong> Protons and neutrons in the nucleus; electrons outside the nucleus.</p></li></ul><h4 id="fa458a4e-4fcf-4456-b924-d133a5c221ff" data-toc-id="fa458a4e-4fcf-4456-b924-d133a5c221ff" collapsed="false" seolevelmigrated="true">Subatomic Particles</h4><table style="min-width: 100px"><colgroup><col style="min-width: 25px"><col style="min-width: 25px"><col style="min-width: 25px"><col style="min-width: 25px"></colgroup><tbody><tr><th colspan="1" rowspan="1" style="text-align:left;"><p>Particle</p></th><th colspan="1" rowspan="1" style="text-align:left;"><p>Charge</p></th><th colspan="1" rowspan="1" style="text-align:left;"><p>Relative Mass</p></th><th colspan="1" rowspan="1" style="text-align:left;"><p>Location</p></th></tr><tr><td colspan="1" rowspan="1" style="text-align:left;"><p>Electron</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>-1</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>1/1840</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>OutsideNucleus</p></td></tr><tr><tdcolspan="1"rowspan="1"style="text−align:left;"><p>Proton</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>+1</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>1</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>Nucleus</p></td></tr><tr><tdcolspan="1"rowspan="1"style="text−align:left;"><p>Neutron</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>0</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>1</p></td><tdcolspan="1"rowspan="1"style="text−align:left;"><p>Nucleus</p></td></tr></tbody></table><h4id="10cfe151−4e5a−4fc4−afde−0b48cf7cac0c"data−toc−id="10cfe151−4e5a−4fc4−afde−0b48cf7cac0c"collapsed="false"seolevelmigrated="true">PeriodicTableInformation</h4><h5id="d95c1db1−8f8d−4b55−9da5−205a9d36a8f0"data−toc−id="d95c1db1−8f8d−4b55−9da5−205a9d36a8f0"collapsed="false"seolevelmigrated="true">KeyInformationDisplayed</h5><ul><li><p>AtomicNumber</p></li><li><p>AtomicSymbol</p></li><li><p>Name</p></li><li><p>RelativeAtomicMass</p></li></ul><h5id="2b5420ce−9c10−4a7f−9461−7b0274bd895b"data−toc−id="2b5420ce−9c10−4a7f−9461−7b0274bd895b"collapsed="false"seolevelmigrated="true">Examples</h5><ul><li><p>Hydrogen(H):Atomicnumber1,relativeatomicmass1.</p></li><li><p>Helium(He):Atomicnumber2,relativeatomicmass4.</p></li><li><p>Lithium(Li):Atomicnumber3,relativeatomicmass7.</p></li><li><p>Beryllium(Be):Atomicnumber4,relativeatomicmass9.</p></li><li><p>Sodium(Na):Atomicnumber11,relativeatomicmass23.</p></li><li><p>Magnesium(Mg):Atomicnumber12,relativeatomicmass24.</p></li></ul><h4id="a3620b42−bbd5−486b−95f6−86dbe9a825e3"data−toc−id="a3620b42−bbd5−486b−95f6−86dbe9a825e3"collapsed="false"seolevelmigrated="true">AtomicNumberandMass</h4><ul><li><p><strong>AtomicNumber:</strong>Thenumberofprotonsinthenucleusofanatom.</p></li><li><p><strong>AtomicMass(RelativeAtomicMass):</strong>Theaveragemassoftheatomsinanelement.</p></li><li><p><strong>ElementSymbol:</strong>Shorthandabbreviationfortheelementname,oftenderivedfromGreekorLatin.</p></li></ul><h4id="1b1f5b8f−b813−40cf−8a64−59208cb581b5"data−toc−id="1b1f5b8f−b813−40cf−8a64−59208cb581b5"collapsed="false"seolevelmigrated="true">ElectronicStructure</h4><ul><li><p>Atomsareneutral(samenumberofprotonsandelectrons).</p></li><li><p>Electronsarrangedinenergylevels(shells).</p></li><li><p>Thenucleuscontainsprotonsandneutronsandistinycomparedtotheatom.</p></li></ul><h4id="48526b46−c344−4daf−bb9b−03ba37e5512e"data−toc−id="48526b46−c344−4daf−bb9b−03ba37e5512e"collapsed="false"seolevelmigrated="true">ElectronShellFilling</h4><ul><li><p>Electronsfillshellsclosesttothenucleus.</p></li><li><p>Shell1:Maximumof2electrons.</p></li><li><p>Shell2:Maximumof8electrons.</p></li><li><p>Shell3:Maximumof8electrons.</p></li><li><p>Shell4:Maximumof2electrons(relevantforthefirst20elements).</p></li></ul><h5id="10f13ccc−2a99−4452−b786−44cfb151d811"data−toc−id="10f13ccc−2a99−4452−b786−44cfb151d811"collapsed="false"seolevelmigrated="true">ElectronicConfigurationsoftheFirst20Elements</h5><ul><li><p>H(1):1</p></li><li><p>He(2):2</p></li><li><p>Li(3):2,1</p></li><li><p>Be(4):2,2</p></li><li><p>B(5):2,3</p></li><li><p>C(6):2,4</p></li><li><p>N(7):2,5</p></li><li><p>O(8):2,6</p></li><li><p>F(9):2,7</p></li><li><p>Ne(10):2,8</p></li><li><p>Na(11):2,8,1</p></li><li><p>Mg(12):2,8,2</p></li><li><p>Al(13):2,8,3</p></li><li><p>Si(14):2,8,4</p></li><li><p>P(15):2,8,5</p></li><li><p>S(16):2,8,6</p></li><li><p>Cl(17):2,8,7</p></li><li><p>Ar(18):2,8,8</p></li><li><p>K(19):2,8,8,1</p></li><li><p>Ca(20):2,8,8,2</p></li></ul><h4id="06f8dbd2−b77b−4e80−ae2e−994bc8391b50"data−toc−id="06f8dbd2−b77b−4e80−ae2e−994bc8391b50"collapsed="false"seolevelmigrated="true">IonsandElectronicStructure</h4><ul><li><p>Ionshaveadifferentnumberofprotonsandelectrons,resultinginanelectricalcharge.</p></li><li><p>Noblegaselementshavestableelectronarrangements.</p></li><li><p>Ionstendtoachievetheelectronstructureofnoblegases.</p></li></ul><h5id="3b7fbd60−73b2−482c−a805−6d63d576db37"data−toc−id="3b7fbd60−73b2−482c−a805−6d63d576db37"collapsed="false"seolevelmigrated="true">ElectricChargeofIons</h5><p>Todeterminetheelectricchargeofanion,comparethenumberofprotons(positivecharge)tothenumberofelectrons(negativecharge).</p><h4id="ef29cf43−c19f−48f2−8c9e−1f0e31d1ff42"data−toc−id="ef29cf43−c19f−48f2−8c9e−1f0e31d1ff42"collapsed="false"seolevelmigrated="true">IonicBonding</h4><h5id="be5a8f33−2615−4426−80e0−5605590e4244"data−toc−id="be5a8f33−2615−4426−80e0−5605590e4244"collapsed="false"seolevelmigrated="true">FormationofIons</h5><ul><li><p>Positiveions(cations)andnegativeions(anions).</p></li><li><p>Ionicbond:Strongelectrostaticattractionbetweenoppositelychargedions.</p></li><li><p>IonicbondsoftenformbetweenGroupIandGroupVIIelements.</p></li></ul><h5id="d600117d−102a−4567−a3e2−76a9128d1f83"data−toc−id="d600117d−102a−4567−a3e2−76a9128d1f83"collapsed="false"seolevelmigrated="true">PropertiesofIonicCompounds</h5><ul><li><p>Highmeltingandboilingpoints.</p></li><li><p>Goodelectricalconductivitywhenaqueousormolten,poorwhensolid.</p></li><li><p>Generallysolubleinwater.</p></li><li><p>Giantlatticestructurewithregulararrangementofalternatingpositiveandnegativeions.</p></li><li><p>Example:Sodiumchloride(NaCl).</p></li></ul><h4id="875e7e80−45a4−4f98−b0d0−1137ec47b4a4"data−toc−id="875e7e80−45a4−4f98−b0d0−1137ec47b4a4"collapsed="false"seolevelmigrated="true">FormationofSodiumChloride(NaCl)</h4><ol><li><p><strong>FormationofSodiumIons(Na+):</strong></p><ul><li><p>Sodiumloses1electrontoachieveafulloutershell.</p></li><li><p></p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>Outside Nucleus</p></td></tr><tr><td colspan="1" rowspan="1" style="text-align:left;"><p>Proton</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>+1</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>1</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>Nucleus</p></td></tr><tr><td colspan="1" rowspan="1" style="text-align:left;"><p>Neutron</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>0</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>1</p></td><td colspan="1" rowspan="1" style="text-align:left;"><p>Nucleus</p></td></tr></tbody></table><h4 id="10cfe151-4e5a-4fc4-afde-0b48cf7cac0c" data-toc-id="10cfe151-4e5a-4fc4-afde-0b48cf7cac0c" collapsed="false" seolevelmigrated="true">Periodic Table Information</h4><h5 id="d95c1db1-8f8d-4b55-9da5-205a9d36a8f0" data-toc-id="d95c1db1-8f8d-4b55-9da5-205a9d36a8f0" collapsed="false" seolevelmigrated="true">Key Information Displayed</h5><ul><li><p>Atomic Number</p></li><li><p>Atomic Symbol</p></li><li><p>Name</p></li><li><p>Relative Atomic Mass</p></li></ul><h5 id="2b5420ce-9c10-4a7f-9461-7b0274bd895b" data-toc-id="2b5420ce-9c10-4a7f-9461-7b0274bd895b" collapsed="false" seolevelmigrated="true">Examples</h5><ul><li><p>Hydrogen (H): Atomic number 1, relative atomic mass 1.</p></li><li><p>Helium (He): Atomic number 2, relative atomic mass 4.</p></li><li><p>Lithium (Li): Atomic number 3, relative atomic mass 7.</p></li><li><p>Beryllium (Be): Atomic number 4, relative atomic mass 9.</p></li><li><p>Sodium (Na): Atomic number 11, relative atomic mass 23.</p></li><li><p>Magnesium (Mg): Atomic number 12, relative atomic mass 24.</p></li></ul><h4 id="a3620b42-bbd5-486b-95f6-86dbe9a825e3" data-toc-id="a3620b42-bbd5-486b-95f6-86dbe9a825e3" collapsed="false" seolevelmigrated="true">Atomic Number and Mass</h4><ul><li><p><strong>Atomic Number:</strong> The number of protons in the nucleus of an atom.</p></li><li><p><strong>Atomic Mass (Relative Atomic Mass):</strong> The average mass of the atoms in an element.</p></li><li><p><strong>Element Symbol:</strong> Shorthand abbreviation for the element name, often derived from Greek or Latin.</p></li></ul><h4 id="1b1f5b8f-b813-40cf-8a64-59208cb581b5" data-toc-id="1b1f5b8f-b813-40cf-8a64-59208cb581b5" collapsed="false" seolevelmigrated="true">Electronic Structure</h4><ul><li><p>Atoms are neutral (same number of protons and electrons).</p></li><li><p>Electrons arranged in energy levels (shells).</p></li><li><p>The nucleus contains protons and neutrons and is tiny compared to the atom.</p></li></ul><h4 id="48526b46-c344-4daf-bb9b-03ba37e5512e" data-toc-id="48526b46-c344-4daf-bb9b-03ba37e5512e" collapsed="false" seolevelmigrated="true">Electron Shell Filling</h4><ul><li><p>Electrons fill shells closest to the nucleus.</p></li><li><p>Shell 1: Maximum of 2 electrons.</p></li><li><p>Shell 2: Maximum of 8 electrons.</p></li><li><p>Shell 3: Maximum of 8 electrons.</p></li><li><p>Shell 4: Maximum of 2 electrons (relevant for the first 20 elements).</p></li></ul><h5 id="10f13ccc-2a99-4452-b786-44cfb151d811" data-toc-id="10f13ccc-2a99-4452-b786-44cfb151d811" collapsed="false" seolevelmigrated="true">Electronic Configurations of the First 20 Elements</h5><ul><li><p>H (1): 1</p></li><li><p>He (2): 2</p></li><li><p>Li (3): 2,1</p></li><li><p>Be (4): 2,2</p></li><li><p>B (5): 2,3</p></li><li><p>C (6): 2,4</p></li><li><p>N (7): 2,5</p></li><li><p>O (8): 2,6</p></li><li><p>F (9): 2,7</p></li><li><p>Ne (10): 2,8</p></li><li><p>Na (11): 2,8,1</p></li><li><p>Mg (12): 2,8,2</p></li><li><p>Al (13): 2,8,3</p></li><li><p>Si (14): 2,8,4</p></li><li><p>P (15): 2,8,5</p></li><li><p>S (16): 2,8,6</p></li><li><p>Cl (17): 2,8,7</p></li><li><p>Ar (18): 2,8,8</p></li><li><p>K (19): 2,8,8,1</p></li><li><p>Ca (20): 2,8,8,2</p></li></ul><h4 id="06f8dbd2-b77b-4e80-ae2e-994bc8391b50" data-toc-id="06f8dbd2-b77b-4e80-ae2e-994bc8391b50" collapsed="false" seolevelmigrated="true">Ions and Electronic Structure</h4><ul><li><p>Ions have a different number of protons and electrons, resulting in an electrical charge.</p></li><li><p>Noble gas elements have stable electron arrangements.</p></li><li><p>Ions tend to achieve the electron structure of noble gases.</p></li></ul><h5 id="3b7fbd60-73b2-482c-a805-6d63d576db37" data-toc-id="3b7fbd60-73b2-482c-a805-6d63d576db37" collapsed="false" seolevelmigrated="true">Electric Charge of Ions</h5><p>To determine the electric charge of an ion, compare the number of protons (positive charge) to the number of electrons (negative charge).</p><h4 id="ef29cf43-c19f-48f2-8c9e-1f0e31d1ff42" data-toc-id="ef29cf43-c19f-48f2-8c9e-1f0e31d1ff42" collapsed="false" seolevelmigrated="true">Ionic Bonding</h4><h5 id="be5a8f33-2615-4426-80e0-5605590e4244" data-toc-id="be5a8f33-2615-4426-80e0-5605590e4244" collapsed="false" seolevelmigrated="true">Formation of Ions</h5><ul><li><p>Positive ions (cations) and negative ions (anions).</p></li><li><p>Ionic bond: Strong electrostatic attraction between oppositely charged ions.</p></li><li><p>Ionic bonds often form between Group I and Group VII elements.</p></li></ul><h5 id="d600117d-102a-4567-a3e2-76a9128d1f83" data-toc-id="d600117d-102a-4567-a3e2-76a9128d1f83" collapsed="false" seolevelmigrated="true">Properties of Ionic Compounds</h5><ul><li><p>High melting and boiling points.</p></li><li><p>Good electrical conductivity when aqueous or molten, poor when solid.</p></li><li><p>Generally soluble in water.</p></li><li><p>Giant lattice structure with regular arrangement of alternating positive and negative ions.</p></li><li><p>Example: Sodium chloride (NaCl).</p></li></ul><h4 id="875e7e80-45a4-4f98-b0d0-1137ec47b4a4" data-toc-id="875e7e80-45a4-4f98-b0d0-1137ec47b4a4" collapsed="false" seolevelmigrated="true">Formation of Sodium Chloride (NaCl)</h4><ol><li><p><strong>Formation of Sodium Ions (Na⁺):</strong></p><ul><li><p>Sodium loses 1 electron to achieve a full outer shell.</p></li><li><p>Na arrow Na^+ + e^-</p></li></ul></li><li><p><strong>FormationofChlorideIons(Cl−):</strong></p><ul><li><p>Chlorinegains1electrontoachieveafulloutershell.</p></li><li><p></p></li></ul></li><li><p><strong>Formation of Chloride Ions (Cl⁻):</strong></p><ul><li><p>Chlorine gains 1 electron to achieve a full outer shell.</p></li><li><p>Cl + e^- arrow Cl^-</p></li></ul></li><li><p><strong>OverallProcess:</strong></p><ul><li><p>Sodiumlosesanelectron,andchlorinegainsit.</p></li><li><p>Oppositelychargedionsattract,formingagiantlattice.</p></li></ul></li></ol><h5id="3aba989d−b5fc−438b−a049−ca64de3f4750"data−toc−id="3aba989d−b5fc−438b−a049−ca64de3f4750"collapsed="false"seolevelmigrated="true">GiantIonicLattice</h5><p></p></li></ul></li><li><p><strong>Overall Process:</strong></p><ul><li><p>Sodium loses an electron, and chlorine gains it.</p></li><li><p>Oppositely charged ions attract, forming a giant lattice.</p></li></ul></li></ol><h5 id="3aba989d-b5fc-438b-a049-ca64de3f4750" data-toc-id="3aba989d-b5fc-438b-a049-ca64de3f4750" collapsed="false" seolevelmigrated="true">Giant Ionic Lattice</h5><p>Na^+andandCl^-ionsareheldtogetherbyelectrostaticforcesina3Dlatticestructure.</p><h4id="4d7288c5−284c−4e2e−bec1−418ff27b72c8"data−toc−id="4d7288c5−284c−4e2e−bec1−418ff27b72c8"collapsed="false"seolevelmigrated="true">PropertiesofIonicCompounds</h4><ul><li><p>Formulaindicatestheratioofions(e.g.,ions are held together by electrostatic forces in a 3D lattice structure.</p><h4 id="4d7288c5-284c-4e2e-bec1-418ff27b72c8" data-toc-id="4d7288c5-284c-4e2e-bec1-418ff27b72c8" collapsed="false" seolevelmigrated="true">Properties of Ionic Compounds</h4><ul><li><p>Formula indicates the ratio of ions (e.g.,MgCl_2implies1Mgatomforevery2chlorineatoms).</p></li><li><p>Highmeltingandboilingpointsduetostrongelectrostaticattractions.</p></li><li><p>Conductelectricityinmoltenordissolvedstatesbecauseionscanmove.</p></li><li><p>Usuallysolubleandsolidsatroomtemperature.</p></li></ul><h4id="d133bafc−9cee−43f5−be96−f9b02835a0e3"data−toc−id="d133bafc−9cee−43f5−be96−f9b02835a0e3"collapsed="false"seolevelmigrated="true">BondingExamples</h4><ol><li><p><strong>MagnesiumOxide(MgO):</strong></p><ul><li><p>Magnesium(2.8.2)loses2electrons.</p></li><li><p>Oxygen(2.6)gains2electrons.</p></li><li><p>implies 1 Mg atom for every 2 chlorine atoms).</p></li><li><p>High melting and boiling points due to strong electrostatic attractions.</p></li><li><p>Conduct electricity in molten or dissolved states because ions can move.</p></li><li><p>Usually soluble and solids at room temperature.</p></li></ul><h4 id="d133bafc-9cee-43f5-be96-f9b02835a0e3" data-toc-id="d133bafc-9cee-43f5-be96-f9b02835a0e3" collapsed="false" seolevelmigrated="true">Bonding Examples</h4><ol><li><p><strong>Magnesium Oxide (MgO):</strong></p><ul><li><p>Magnesium (2.8.2) loses 2 electrons.</p></li><li><p>Oxygen (2.6) gains 2 electrons.</p></li><li><p>Mg^{2+}andandO^{2-}.</p></li></ul></li><li><p><strong>SodiumFluoride(NaF):</strong></p><ul><li><p>Sodium(2.8.1)loses1electron.</p></li><li><p>Fluorine(2.7)gains1electron.</p></li><li><p>.</p></li></ul></li><li><p><strong>Sodium Fluoride (NaF):</strong></p><ul><li><p>Sodium (2.8.1) loses 1 electron.</p></li><li><p>Fluorine (2.7) gains 1 electron.</p></li><li><p>Na^+[2.8]andandF^-[2.8].</p></li></ul></li><li><p><strong>LithiumOxide(.</p></li></ul></li><li><p><strong>Lithium Oxide (Li_2O):</strong></p><ul><li><p>Twolithiumatomseachlose1electron.</p></li><li><p>Oneoxygenatomgains2electrons.</p></li><li><p>):</strong></p><ul><li><p>Two lithium atoms each lose 1 electron.</p></li><li><p>One oxygen atom gains 2 electrons.</p></li><li><p>2Li^+andandO^{2-}.</p></li></ul></li><li><p><strong>LithiumNitride(.</p></li></ul></li><li><p><strong>Lithium Nitride (Li_3N):</strong></p><ul><li><p>Threelithiumatomseachlose1electron.</p></li><li><p>Onenitrogenatomgains3electrons.</p></li><li><p>):</strong></p><ul><li><p>Three lithium atoms each lose 1 electron.</p></li><li><p>One nitrogen atom gains 3 electrons.</p></li><li><p>3Li^+andandN^{3-}.</p></li></ul></li><li><p><strong>AluminumFluoride(.</p></li></ul></li><li><p><strong>Aluminum Fluoride (AlF_3):</strong></p><ul><li><p>Onealuminumatomloses3electrons.</p></li><li><p>Threefluorineatomseachgain1electron.</p></li><li><p>):</strong></p><ul><li><p>One aluminum atom loses 3 electrons.</p></li><li><p>Three fluorine atoms each gain 1 electron.</p></li><li><p>Al^{3+}andand3F^{-}.</p></li></ul></li></ol><h4id="683cf431−6111−47ec−bca8−9c4f5fc5c368"data−toc−id="683cf431−6111−47ec−bca8−9c4f5fc5c368"collapsed="false"seolevelmigrated="true">CovalentBonding</h4><h5id="9fb0adf1−d981−4069−b196−4196c38c11cb"data−toc−id="9fb0adf1−d981−4069−b196−4196c38c11cb"collapsed="false"seolevelmigrated="true">Definition</h5><ul><li><p>Covalentbond:Formedwhenapairofelectronsissharedbetweentwoatoms.</p></li><li><p>Typicallyoccursbetweennon−metal+non−metalorhydrogen+non−metal.</p></li><li><p>Leadstonoblegaselectronicconfigurations.</p></li></ul><h5id="5b697edd−6428−43d8−b20d−5156f81e477f"data−toc−id="5b697edd−6428−43d8−b20d−5156f81e477f"collapsed="false"seolevelmigrated="true">PropertiesofSimpleCovalentCompounds</h5><ul><li><p>Lowmeltingandboilingpoints.</p></li><li><p>Oftenliquidsorgasesatroomtemperature.</p></li><li><p>Poorelectricalconductivity.</p></li><li><p>Weakintermolecularforces(easytobreak)comparedtostrongcovalentbondswithinthemolecules.</p></li></ul><h5id="0322cff3−2d80−4041−942d−745e48938bbb"data−toc−id="0322cff3−2d80−4041−942d−745e48938bbb"collapsed="false"seolevelmigrated="true">FormationofHydrogen(.</p></li></ul></li></ol><h4 id="683cf431-6111-47ec-bca8-9c4f5fc5c368" data-toc-id="683cf431-6111-47ec-bca8-9c4f5fc5c368" collapsed="false" seolevelmigrated="true">Covalent Bonding</h4><h5 id="9fb0adf1-d981-4069-b196-4196c38c11cb" data-toc-id="9fb0adf1-d981-4069-b196-4196c38c11cb" collapsed="false" seolevelmigrated="true">Definition</h5><ul><li><p>Covalent bond: Formed when a pair of electrons is shared between two atoms.</p></li><li><p>Typically occurs between non-metal + non-metal or hydrogen + non-metal.</p></li><li><p>Leads to noble gas electronic configurations.</p></li></ul><h5 id="5b697edd-6428-43d8-b20d-5156f81e477f" data-toc-id="5b697edd-6428-43d8-b20d-5156f81e477f" collapsed="false" seolevelmigrated="true">Properties of Simple Covalent Compounds</h5><ul><li><p>Low melting and boiling points.</p></li><li><p>Often liquids or gases at room temperature.</p></li><li><p>Poor electrical conductivity.</p></li><li><p>Weak intermolecular forces (easy to break) compared to strong covalent bonds within the molecules.</p></li></ul><h5 id="0322cff3-2d80-4041-942d-745e48938bbb" data-toc-id="0322cff3-2d80-4041-942d-745e48938bbb" collapsed="false" seolevelmigrated="true">Formation of Hydrogen (H_2)</h5><ul><li><p>Nucleirepelbutareattractedtosharedelectrons.</p></li></ul><h4id="ad331c57−b9bb−4bf0−982c−b1b6a08012f0"data−toc−id="ad331c57−b9bb−4bf0−982c−b1b6a08012f0"collapsed="false"seolevelmigrated="true">CovalentBondFormation</h4><ul><li><p>Nonmetalssharevalenceelectronstoachieveanoblegasconfiguration.</p></li><li><p>Example:Fluorine(F)has7valenceelectronsandsharesoneelectronwithanotherfluorineatomtoformacovalentbond.</p></li></ul><h4id="16ef4e54−ac4d−4c78−a715−98eab011ca51"data−toc−id="16ef4e54−ac4d−4c78−a715−98eab011ca51"collapsed="false"seolevelmigrated="true">SingleCovalentBond</h4><ul><li><p>Sharingoftwovalenceelectrons.</p></li><li><p>Occursbetweennonmetalsandhydrogen.</p></li><li><p>Formsactualmolecules,unlikeionicbonds.</p></li><li><p>Twospecificatomsarejoined.</p></li></ul><h4id="c8785f3e−2a3a−4dd0−96be−73fdd6cd2f63"data−toc−id="c8785f3e−2a3a−4dd0−96be−73fdd6cd2f63"collapsed="false"seolevelmigrated="true">HowtoShowCovalentBondFormation</h4><ol><li><p>Determinethefinalformula.</p></li><li><p>Putthepiecestogethertoachievetherightformula.</p></li></ol><h5id="2675a3b8−a9e3−4130−aa3e−c05063c89d4b"data−toc−id="2675a3b8−a9e3−4130−aa3e−c05063c89d4b"collapsed="false"seolevelmigrated="true">Example:Water()</h5><ul><li><p>Nuclei repel but are attracted to shared electrons.</p></li></ul><h4 id="ad331c57-b9bb-4bf0-982c-b1b6a08012f0" data-toc-id="ad331c57-b9bb-4bf0-982c-b1b6a08012f0" collapsed="false" seolevelmigrated="true">Covalent Bond Formation</h4><ul><li><p>Nonmetals share valence electrons to achieve a noble gas configuration.</p></li><li><p>Example: Fluorine (F) has 7 valence electrons and shares one electron with another fluorine atom to form a covalent bond.</p></li></ul><h4 id="16ef4e54-ac4d-4c78-a715-98eab011ca51" data-toc-id="16ef4e54-ac4d-4c78-a715-98eab011ca51" collapsed="false" seolevelmigrated="true">Single Covalent Bond</h4><ul><li><p>Sharing of two valence electrons.</p></li><li><p>Occurs between nonmetals and hydrogen.</p></li><li><p>Forms actual molecules, unlike ionic bonds.</p></li><li><p>Two specific atoms are joined.</p></li></ul><h4 id="c8785f3e-2a3a-4dd0-96be-73fdd6cd2f63" data-toc-id="c8785f3e-2a3a-4dd0-96be-73fdd6cd2f63" collapsed="false" seolevelmigrated="true">How to Show Covalent Bond Formation</h4><ol><li><p>Determine the final formula.</p></li><li><p>Put the pieces together to achieve the right formula.</p></li></ol><h5 id="2675a3b8-a9e3-4130-aa3e-c05063c89d4b" data-toc-id="2675a3b8-a9e3-4130-aa3e-c05063c89d4b" collapsed="false" seolevelmigrated="true">Example: Water (H_2O)</h5><ul><li><p>Eachhydrogenhas1valenceelectronandwants1more.</p></li><li><p>Oxygenhas6valenceelectronsandwants2more.</p></li><li><p>Theysharetomakeeachother"happy"(fullvalenceshell).</p></li></ul><h4id="87faefde−e28f−4f8c−8ea5−c2d8b1408782"data−toc−id="87faefde−e28f−4f8c−8ea5−c2d8b1408782"collapsed="false"seolevelmigrated="true">MultipleBonds</h4><ul><li><p>Atomscansharemorethanonepairofvalenceelectrons.</p></li><li><p>Doublebond:Atomssharetwopairs(4)ofelectrons.</p></li><li><p>Triplebond:Atomssharethreepairs(6)ofelectrons.</p></li></ul><h5id="cc198325−2325−4668−a918−f760ad6a7e9d"data−toc−id="cc198325−2325−4668−a918−f760ad6a7e9d"collapsed="false"seolevelmigrated="true">Example:CarbonDioxide()</h5><ul><li><p>Each hydrogen has 1 valence electron and wants 1 more.</p></li><li><p>Oxygen has 6 valence electrons and wants 2 more.</p></li><li><p>They share to make each other "happy" (full valence shell).</p></li></ul><h4 id="87faefde-e28f-4f8c-8ea5-c2d8b1408782" data-toc-id="87faefde-e28f-4f8c-8ea5-c2d8b1408782" collapsed="false" seolevelmigrated="true">Multiple Bonds</h4><ul><li><p>Atoms can share more than one pair of valence electrons.</p></li><li><p>Double bond: Atoms share two pairs (4) of electrons.</p></li><li><p>Triple bond: Atoms share three pairs (6) of electrons.</p></li></ul><h5 id="cc198325-2325-4668-a918-f760ad6a7e9d" data-toc-id="cc198325-2325-4668-a918-f760ad6a7e9d" collapsed="false" seolevelmigrated="true">Example: Carbon Dioxide (CO_2)</h5><ul><li><p>Carbon(centralatom)has4valenceelectronsandwants4more.</p></li><li><p>Oxygenhas6valenceelectronsandwants2more.</p></li><li><p>Requirestwodoublebonds.</p></li></ul><h5id="79eaedb7−aabf−49e0−9dc7−1430d40e17da"data−toc−id="79eaedb7−aabf−49e0−9dc7−1430d40e17da"collapsed="false"seolevelmigrated="true">Example:Ammonia()</h5><ul><li><p>Carbon (central atom) has 4 valence electrons and wants 4 more.</p></li><li><p>Oxygen has 6 valence electrons and wants 2 more.</p></li><li><p>Requires two double bonds.</p></li></ul><h5 id="79eaedb7-aabf-49e0-9dc7-1430d40e17da" data-toc-id="79eaedb7-aabf-49e0-9dc7-1430d40e17da" collapsed="false" seolevelmigrated="true">Example: Ammonia (NH_3$$)

      • Nitrogen (N) has 5 valence electrons and wants 3 more.

      • Hydrogen (H) has 1 valence electron and wants 1 more.