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1 - 11: Atoms and Proton number, Nucleon number 12 - 17: Isotopes 18-23: Electron shells 24: Elements, compounds and mixtures 25-28: Ions and ionic bonding 29-41: Covalent bonding 42-43: Properties of ionic compounds and covalent compounds 44-48: Giant covalent structures
Key terms to remember (Anion, Cation)
Anion: Negative ion
Cation: Positive ion
What does an atom contain?
An atom has a nucleus, containing protons and neutrons, and electrons that orbit the nucleus.
What is the charge and relative mass of proton, neutron and electron?
Proton: Relative mass: 1, charge: +1
Neutron: Relative mass: 1, charge: neutral (0)
Electron: Relative mass: nearly 0, charge: -1
Where is the nucleus?
What is the charge of the nucleus?
What is the mass and the size of the nucleus compared to the atom?
The nucleus is in the middle of the atom.
The nucleus has a positive charge because it contain proton.
The mass of the nucleus is almost the whole mass of the atom, however compared to the overall size of the atom, the nucleus is tiny.
Where are the electrons?
What is the charge of electron?
Their size and orbitals?
The mass of it?
Electrons move around the nucleus in energy levels called shells.
Electron are negatively charged.
They’re tiny, but their orbitals cover a lot of space.
The size of their orbitals determines the size of the atom.
Electron have virtually no mass.
The charge of a neutral atom?
No charge (0) overall
The relationship of the number of protons and electrons in a neutral atom?
The number of protons and electrons are equal.
What is an atom that lose/gain electrons (doesn’t has the same number of protons and electrons) called?
The atom become charged and it’s called an ion
What is proton (atomic) number and nucleon (mass) number?
The proton/atomic number is the number of protons in an atom’s nucleus.
The nucleon/mass number is the total number of protons and neutrons in an atom’s nucleus
Atoms of the same element have the same number of protons?
Yes
How to find the number of neutrons based on proton number and nucleon number?
Subtract proton number by nucleon number..
What is an isotope?
Isotopes are atoms of the same element (same number of protons) but different number of neutrons.
Popular pair of isotopes: Carbon-12 and Carbon-13
The properties of the isotopes of the same element?
They have the same properties - They’ll react in the same way
What is the relative atomic mass Ar (related to isotope)?
Ar - relative atomic mass is the average mass of all the isotopes of the element.
How to find the relative atomic mass of an element?
Multiply each relative isotopic mass by its isotopic abundance.
Add up the results.
Divide by the sum of the abundances.
Boron has two isotopes: Boron-10 and Boron-11.
The abudance of boron-10 is 4 and boron-11 is 6.
Find Ar of Boron.
(10×4 + 11×16)/(4+16) = 216/20
= 10.8
Where do electrons orbit around the nucleus?
What is the number of electrons in each shell?
Electrons always occupy shells or energy levels.
First shell: 2, Second shell: 8, Third shell: 8
What is the role of the outer shell electrons?
Why does atom form bonds?
Why group VIII elements are unreactive?
The outer shell electrons control Reactivity.
Atoms will form bonds with other atoms to have a full outer shell.
Group VIII elements are unreactive as they already have a full outer shell.
In a neutral atom, the numbers of electrons and protons are equal.
Notation of electronic configuration?
There’re 2 ways:
Diagrams
Numbers
How to find electronic configuration by proton/atomic number
The numbers of electrons and protons are equal.
How to find electronic configuration by Periodic table?
The period displays the number of shells.
The group displays the number of electron in the outer shell.
We can just find the electronic configuration of first 20 elements, the others are a bit tricky.
Distinguish elements, compounds and mixtures
Elements are one type of atoms
Compounds are two or more type of atoms chemically bonded together
Mixtures are the mix of differently type of atoms, only physical changes but no chemical changes.
What are ions?
What is ionic bonding?
Ions are the charged particles.
Ionic bonding is the bonding between a metal and a non-metal where non-metal gain electron and metal lose electron.
Metal or non-metal tend to lose electron, gain electron?
Metal: Lose electrons, to become positively charged ion called cation.
Non-metal: Gain electrons, to become negatively charged ion called anion.
Dot and cross diagram for ionic compound (NaCl)
Do ionic compounds have a giant lattice structure?
Compounds with ionic bonding always have giant lattice structures.
The ions are held together in a closely packed 3D lattice arrangement by the attraction between oppositely charged ions.
These lattices structures are a regular arrangement of alternating positive and negative ions.
What is covalent bonding?
Covalent bonding involves what to make atoms have the full outer shell?
What is molecule?
Covalent bonding is the bonding between non-metal and non-metal.
Convalent bonding involves the sharing of electrons between the non-metals.
Each covalent bond provides one extra shared electron for each atom.
Molecules is a type of covalent bonding between two same non-metals.
The sharing of electrons
The atoms share electrons by pair:
one pair of electrons (single bond)
two pairs of electrons (double bond)
three pairs of electrons (triple bond)
What is the structure of Hydrogen?
H2, a pair of electrons is shared between the hydrogen atoms (single bond).
What is the structure of Chlorine?
Cl2, a pair of electrons is shared between the Chlorine atoms (single bond).
What is the structure of Hydrochloric acid?
HCl, a pair of electrons is shared between Hydrogen and Chlorine atom (single bond)
What is the structure of Water?
H2O, form 2 covalent bonds, two hydrogen atoms share a pair of electrons with an oxygen atom.
What is the structure of Ammonia?
NH3, form 3 covalent bonds, three hydrogen atoms share a pair of electrons with an nitrogen atom.
What is the structure of methane?
CH4, form 4 covalent bonds, 4 hydrogen atoms share a pair of electrons with a Carbon atom.
What is the structure of Carbon dioxide?
CO2, form 2 double covalent bonds, 2 oxygen atoms form two pair of electrons with a carbon atom.
What is the structure of Nitrogen?
N2, form a triple covalent bond
What is the structure of Oxygen?
O2, form a double covalent bond
What is the structure of Methanol (CH3OH)?
CH3OH, is kinda complicated
What is the structure of Ethane?
C2H4, Two carbon atoms form a doule covalent bond and each carbon atom form a single bond with two hydrogen atoms.
List the properties of ionic compounds and explain why.
Hint: 2 properties
High melting points and high boiling points, and do not readily form gases (they aren’t very volatile)
Because the ionic bonds are extremely strong. It takes a lot of energy to break the bonds to seperate ions.
Doesn’t not conduct electricity in Solid but conduct in Liquid.
Because the ions are held in place and not free to move when they’re in solid. When ionic compounds melt or dissolve, the ions are free to move and carry electric charge.
List the properties of simple molecular substances (simple covalent bond) and explain why.
Hint: 2 properties
Low melting points and low boiling points.
The atoms are hold together by strong bonds but the forces between molecules, intermolecular forces are weak.
To melt or boil simple molecules, just need to break the weak intermolecular forces.
Don’t conduct electricity
it’s because they aren’t charged, so there’re no free electrons or ions.
What create the giant covalent structures? (ionic bonding or covalent bonding)
Covalent bonding
Certain properties of most giant covalent structures?
In giant covalent structures, all the atoms are bonded to each other by strong covalent bonds.
Very high melting and boiling points (lots of energy needed to break strong covalent bonds).
Don’t contain charged particles, don’t conduct electricity.
Aren’t soluble in water.
The structure of graphite?
The properties of graphite?
Why graphite can conduct electricity?
Each carbon atom forms 3 covalent bonds, creating sheets of hexagons, those covalent bonds need a lot of energy to break, so graphite have a high melting point.
No covalent bonds between layers, so they’re free to move. over each other. This makes graphite soft and slippery, so it’s ideal as a lubricating material.
Only 3/4 carbon’s outer electrons are used in bonds, so each carbon atom has one delocalised electron (free), which make carbon electricity conductive.
The structure of Diamond?
The properties of Diamond?
What is diamond used for?
Each carbon atom form 4 covalent bonds. So there’s no free/delocalised electron → diamond don’t conduct electricity.
Diamond has a rigid lattice structure.
Diamond has no weak intermolecular forces, so it’s really hard - it’s used to strengthen cutting tools.
What is silicon dioxide?
Structure of silicon dioxide?
Properties compared to diamond?
Silicon (IV) oxide (or silicon dioxide, SiO2) has a giant covalent structure very similar to diamond.
The silicon atoms are positioned like the carbon atoms in diamond, with an oxygen atom between each one.
Silicon share many properties with diamond. it’s hard, has a high melting point and has no free electrons (doesn’t conduct electricity).
Note
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