the periodic table + bonding

what is an atom?

smallest particle of a chemical element that can exist

what is a molecule?

two or more atoms chemically bonded together

what is the relative charge and mass of a proton neutron and electron

proton relative charge = 1
proton relative mass = 1

neutron relative charge = 0

neutron relative mass = 1

electron relative charge = -1

electron relative mass = 1/1836

what is the atomic number?

number of protons/electrons

what is the mass number?

the total number of protons and neutrons

what is the nucleon number?

same as mass number ie. total number of protons and neutrons

how is the number of protons/electrons in an atom calculated

same as atomic number

how is the number of neutrons in an atom calculated?

mass number - atomic number

what is an isotope?

atoms of the same element with the same number of protons but different numbers of neutrons

what is the relative atomic mass?

the ratio of the average mass of one atom of an element compared with 1/12th of the mass of an atom of carbon-12

how do you calculate the Ar of an element from the relative abundance of a particular isotope?

(% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2)/100

describe the layout of the periodic table

elements arranged in order of atomic number

hydrogen by itself

metals found left of stepped line

non-metals found right of stepped line

what is the period number of the periodic table?

tells you the number of shells of electrons

what is the group number of the periodic table?

tells you the number of electrons in the outer shell

eg. F has 7 electrons in its outer shell and is therefore in group 7

give the electronic configurations of sodium, oxygen, chlorine and magnesium

Na = 2,8,1

O = 2,6

Cl = 2,8,7

Mg = 2,8,2

Define malleable

may be hammered into shape

define ductile

may be drawn into a wire

describe the properties of metals

good conductors of heat and electricity

shiny

malleable

sonorous

ductille

form positive ions in ionic compounds

partake in ionic bonding

form basic oxides

solids at room temperature (except mercury)

describe the properties of non-metals

poor conductors

brittle

form negative ions in ionic compounds

partake in ionic and covalent bonding

form acidic oxides

why do elements in the same group have similar properties?

same number of electrons in outer shell

why are noble gases (group 0) unreactive?

they have a full outer shell of electrons

stable

how is an ion formed?

an atom loses or gains electrons

loses electron —→ forms positive ion

gains electron —→ forms negative ion

when working out the charge on an ion, remember:

for groups 1-3, the charge on the ion is the same as the group number

eg. Mg is in group 2 and therefore forms Mg 2+

for groups 5,6,7, the charge on the ion is 8 - group number

eg. N is in group 5 8-5 = 3 , there for N 3-

what are some positive ions (cations)

H+

Ag+

Cu2+

Fe2+

Fe3+

Pb2+

Zn2+

NH4

what are some negative ions (anions)?

OH-

NO3-

CO3^2-

SO4²-

what is an ionic bond?

electro static force of attraction between oppositely charged ions

• forms between a metal and a non-metal

give the properties of giant ionic lattices

high melting and boiling points

conduct electricity when molten/dissolved in aqueous solution

brittle

why do ionic structures have high melting and boiling points?

form giant ionic lattices

strong electro static forces of attraction between oppositely charged ions

requires lots of energy to break

why dont ionic substances conduct electricity when solid?

ions are held tightly in fixed positions

not free to move

why do ionic substances conduct electricity when molten/dissolved?

ions are free to move

can carry electric charge

explain why ionic substances are brittle

applying force causes ions to move

like charges align and repel

lattice structure breaks apart

what is a covalent bond?

basic definition: a pair of electrons shared between two atoms

detailed definition: strong electrostatic forces of attraction between nuclei (positively charged) and shared pair of electrons (negatively charged)

form between two non-metals

what is a simple molecular substance?

small, covalently bonded molecule

H2O CO2

define intermolecular force

temporary weak attraction between different molecules

why do simple molecular substances have low melting points?

weak intermolecular forces of attraction

do not require a lot of energy to overcome

why does the boiling point of simple molecular substances increase with increasing relative molecular mass?

boiling overcomes the intermolecular forces of attraction between molecules

greater Mr = greater intermolecular forces of attraction to be overcome

more heat energy needed to overcome these forces

why dont simple molecular substances conduct electricity?

no overall electric charge

no free electrons

define giant covalent structure

large lattice of covalently bonded atoms

eg. graphite silicon dioxide

what is an allotrope?

different forms of the same element in the same physical state

give 3 allotropes of carbon

diamond

graphite

C60 fullerene

why does diamond have such a high melting point?

giant covalent structure

each carbon atom covalently bonded to 4 others

many strong covalent bonds

require lots of energy to break

why dont most covalent substances conduct electricity?

no free electrons

each electron in outer shell is bonded

why doesnt diamond conduct electricity?

no free electrons

each electron in outer shell is bonded

why does graphite have such a high melting point?

many strong covalent bonds

require lots of energy to break

why does graphite conduct electricity?

each carbon atom is only bonded to 3 others

4th electron free to move - delocalised pool of electrons

why is graphite used as lubricant?

carbon atoms are arranged in layers

layers held together by weak intermolecular forces

do not require a lot energy to break

layers slide off eachother

why does C60 fullerene have a lower melting and boiling point than graphite and diamond?

simple molecular structure

weak intermolecular forces

require little energy to break

why does C60 fullerene not conduct electricity?

although each carbon atom is only bonded to 3 others, 4th electron not free to move

stays within each C60 molecule