Unit 1 review

Matter

anything that has a mass and takes up space

atomic radius

• measure of the size of an atom

• usually in pm

• distance from the center of an atom to the outermost electrons

atomic radius across a row

• same energy levels

• least number of protons = less attraction from electrons = greater atomic radius

atomic radius within a group

• more energy levels are added

• each additional level is a greater distance from the nucleus

  • electrons of the inner levels shield the outer electrons from the full charge of the nucleus so the outer electrons are not as strongly attracted

1st ionization energy

the minimum amount of energy required to remove the outermost electron from a neutral atom in a gaseous state

ionization energy explaination

• atomic radius decreases so the pull on outermost electrons increases

• increased pull = harder to remove

• tight

electron affinity

energy change that occurs when an electron is added to a neutral atom in the gaseous state

electronegativity

a measure of an atom’s ability to attract electrons in a chemical bond

electronegativity and bond type

• <0.5 covalent

• 0.5-1.7 polar covalent

• >1.7 ionic

ionic bond

• bond between a positive ion and a negative ion

• a result of the electrostatic force between oppositely charged ions

properties of ionic compounds

• hard

• brittle

• high melting points

• conduct electricity as molten liquids or when dissolved in water

covalent bond

• atoms share an electron pair

• usually unequal sharing (due to electronegativity)

properties of covalent compounds

• variety of textures

• low melting/boiling points

• most do not dissolve in water

• usually non-electrolytes

States of molecular compounds

• molecualr elements are gases (except Br2 I2)

• C6H1206 glucouse is solid

valence electrons

an electron in the outermost energy level or orbit

non-polar covalent bond

a covalent bond formed between atoms with identical/ very similar electronegativities

polar covalent bond

a covalent bond formed between atoms with significantly different electronegativities resulting in a bond with localized positive and negative charges or poles

octet rule

when atoms combine the tend to achieve 8 valence electrons

isoelectronic

having the same number of electrons or identical electron configurations

diatomic element

each molecule is made of 2 of the same atoms N2 O2

molecular element

consists of molecules containing atoms of only one type N2 S8

molecular compound

each molecule is made up of a least 2 different elements H20 C6H12O6

isotope

form of element in which the atoms have the same number of protons, but a different number of neutrons

atomic number

mass number

electrolyte

• a substance that conducts electricity in solution

• any soluble salt (ionic) will form an electrolyte in aqueous solution

contributions of the ancient greeks to atomic theory

• Democritus reasoned that matter would eventually become indivisible (atomos)

• But, Aristotle favored Empedocles’ theory (EAWF) which was more popular for 2000 years

contributions of the alchemists to atomic theory

• glassware, equipment, handling procedures and alloys

• allowed for development of modern science

John Dalton

• early 1800

• Billiard ball model

• rejected- atoms are not solid indivisble spheres, did not address how electrical charge is aquired, Thomson proved it was divisible when he discovered the electron

• proposed first modern atomic theory

JJ Thomson

• 1897

• plum pudding model

• rejected- said electrons are spaced evenly in a positive solid sphere

• discovered electron

Rutherford

• early 1900

• nuclear model

• modified - bohr added quantitzed energy levels that couldn’t be accounted for with classical physics

• discovered the positively charged, small, dense nucleus (gold foil experiement)

Bohr

• 1913

• planetary model

• modified- stated electrons move in planetary orbits, shrodinger modified into 3D orbitals

• discovered energy levels explained why excited electrons emit specific line spectra when returning to ground state

Chadwick

• 1932

• Discovered the neutron

Schrodinger

• 1926

• Quantum mechanical model

• represents our current understanding of atomic orbital structures

• applied wave mechanics to show that electrons exist in orbitals

Gold foil experiement expected results

• all positively charged alpha particles pass directly through gold foil

• thomson’s model had a uniform positive charge that would be too weak to repel

Gold foil experiement actual results

• 1 in 20 000 particle was deflected

• the alpha particles hit a dense, heavy, positively charged nucleus

• the majority passed through because an atom is mostly empty space

tetrahedral

• 4 single bonds no lone pairs

• usually carbon

• 109.5

trigonal pyramidal

• 3 single bonds 1 lone pair

• usually nitrogen/phosphorus with hydrogen/halogens

• 107.3

bent

• 2 single bonds 2 lone pairs

• oxygen/sulfur with hydrogen/halogens

• 104.5

trigonal planar

• 4 bonding pairs ( 1 double 2 single)

• 120

linear