General Review Chemistry

Question 1

what does the valence of an atom determine?
why?

Answer 1

the valence determines an atom’s reactivity.

this is because the amount of electrons it needs to complete the valence shell determines how much and how likely it is to react with other atoms. it also determines which kinds of bonds an atom will make. atoms with a smaller valence are more likely to lose their lonely electrons because there is less gravitational pull from the nucleus keeping them in orbit, therefore they are more easily lost.

Question 2

where are protons found and what is their mass and charge?

where are neutrons found and what is their mass and charge?

where are electrons found and what is their mass and charge?

Answer 2

protons are found in the nucleus of the atom, their relative mass is 1, and their charge is positive.

neutrons are found in the nucleus of the atom, their relative mass is 1, and their charge is 0 - they are neutral.

electrons are found orbiting the nucleus of an atom, their relative mass is 2000 times smaller than a proton or neutron, and their charge is -1.

Question 3

on a periodic table, what does the group tell you?

on a periodic table, what does the period tell you?

Answer 3

the group is the number of valence electrons an element has.

the period is the number of electron shells an element has.

Question 4

what is group one on the periodic table?
what makes this group interesting?

Answer 4

Alkali Metals.
the fact that they have only one valence electron, making them extremely reactive - they must be kept in oil because they react with oxygen and water.

Question 5

how are group one metals different from other metals?

Answer 5

they have a higher density, meaning that they float.
they are soft and malleable.
they have low melting and boiling points.

Question 6

what are elements in group 7 called?

Answer 6

halogens

Question 7

what is the definition of a displacement reaction?

Answer 7

when a more reactive halogen displaces a less reactive halogen in a chemical reaction, leaving the lesser one free, on its own.

Question 8

as you move down the group, what trend can be observed with halogens?

Answer 8

the melting and boiling points of halogens increase as you move downwards because the atomic radii increases by one shell as you go down, and the intermolecular force between atoms increases, requiring more force to break them apart.

Question 9

what three reactions do halogens form?

Answer 9

• displacement reactions
• reactions with metals
• reactions with hydrogen (gas)

Question 10

what is the name of elements in group 8?

Answer 10

noble gases.

Question 11

what is special about group 8 elements?

Answer 11

they are inert as their valence is full. this means that they do not need to interact with other elements to fulfill their valence. this means that they hardly interact with other elements. they are usually on their own.

Question 12

what three types of bonding have we gone over? give brief definitions of each.

Answer 12

• ionic - a transaction of electrons between metals (low valence) and non-metals (high valence). metal ions lose electrons, becoming positively charged (cations) and non-metals recieve the electrons, becoming negatively charged (anions). the positive and negative charges of the ions keep the bonds strong, with strong intermolecular forces because of the electromagnetic force.
• covalent - the sharing of electrons. this happens between non-metals. weak intermolecular forces as there is a neutral charge, but strong bonds between atoms.
• metallic - a lattice structure of positively charged ions surrounded by a sea of delocalised electrons. occurs between metals. strong intermolecular forces because of the attraction due to charges.

Question 13

what are the properties of ionic compounds?

Answer 13

• high melting and boiling points - due to high levels of energy required to break strong intermolecular forces
• solid at room temperature - again, room temp (25˚C) not enough to break bonds
• brittle - due to structure and arrangement. if hit the compound will break, following the crystal pattern.
• conducts when dissolved - because the ions are broken apart when dissolved, an electrical current uses the ions to flow through

Question 14

what are the properties of covalent compounds?

Answer 14

• low melting and boiling points - due to weak intermolecular forces low energy levels needed to break apart molecules.
• does not conduct - no charge for free flowing electrons to pass through
• usually gaseous - weak intermolecular forces allow for molecules to flow over each other easily

Question 15

what are the properties of metallic compounds?

Answer 15

• high melting and boiling points - due to strong intermolecular forces
• malleable - ions can slide over each other without breaking
• conductive - allows for a current to pass through because of free flowing ions and delocalised electrons

Question 16

what is the definition of an allotrope?
give two exaples for carbon

Answer 16

the same element but arranged differently.
diamond and graphite

Question 17

what is the definition of a giant covalent structure?

Answer 17

lots of non-metal atoms joined to each other by strong covalent bonds in a giant lattice structure.

Question 18

what are the properties of diamond?

Answer 18

• extremely high melting and boiling points - due to incredibly strong bonds, no weak intermolecular forces because it is essentially one molecule
• does not conduct
• extremely hard and dense because each carbon is bonded to four other carbons in a tetrahedron shape

Question 19

what are the properties of graphite?

Answer 19

• each carbon is bonded to three others, leaving a free electron for each atom in layers
• this electron makes it possible for graphite to conduct
• slippery - layers are only connected by weak intermolecular forces, therefore they can slip and slide over each other
• extremely high melting and boiling points