2 Atoms, elements and compounds

Question 1

elements

Answer 1

simplest structure that cannot be broken down into smaller parts or changed into another substance.

Question 2

Compound

Answer 2

a substance made from two or more different elements that have been chemically joined

Question 3

mixture

Answer 3

a combination of two or more substances (elements or compounds) that are not chemically combined

Question 4

atom structure

Answer 4

a central nucleus containing neutrons and protons surounded by electrons in shells

Question 5

relative charges of proton, neutron and an electron

Answer 5

Electron is -1
Proton is +1
neutron is 0

Question 6

relative masses of proton, neutron and an electron

Answer 6

Electron is 1/1835
Proton is 1
Neutron is 1

Question 7

proton/atomic number

Answer 7

number of protons in the nucleus of an atom

Question 8

mass/nucleon number

Answer 8

the total number of protons and neutrons in the nucleus of an atom

Question 9

isotopes

Answer 9

different atoms of the same element that have the same number of protons by different numbers of neutrons

Question 10

chemical properties of isotopes

Answer 10

isotopes of the same element have same chemical properties because they have the same number of electrons and therefore the same electronic configuration

Question 11

relative atomic mass formula

Answer 11

(abundance x mass number)/100

Question 12

cations

Answer 12

positive ions

Question 13

anions

Answer 13

negative ions

Question 14

ionic bond

Answer 14

a strong electrostatic attraction between oppositely charged ions

Question 15

ionic compounds properties

Answer 15

high melting and boiling points
good electrical conductivity when aqueous or molten and poor when solid

Question 16

giant lattice structure of ionic compound

Answer 16

regular arrangement of alternating positive and negative ions

Question 17

why do ionic compounds have high melting points?

Answer 17

have strong electrostatic forces of attraction between oppositely charged ions. Large amounts of energy are needed to break the many strong bonds.

Question 18

why are ionic compounds a good conductor of electricty when liquid?

Answer 18

Because their ions are free to move from place to place

Question 19

How are covalent bonds formed

Answer 19

when a pair of electrons is shared between two atoms leading to a full shell

Question 20

why do simple molecular bonds have low melting and boiling points

Answer 20

The have weak intermolecular forces between molecules, low energy is required to break them

Question 21

why do simple molecular structures have poor electrical conductivity

Answer 21

no free ions that can move

Question 22

diamond

Answer 22

each carbon atom is covalently bonded to 4 other carbon atoms
- tetrahedral
- high m.p and b.p
- no conduction of electricity

Question 23

graphite

Answer 23

each carbon atom is covalently bonded with 3 other carbon atoms, resulting in a delocalised electron
- flat sheets
- high m.p and b.p
- can conduct electricity

Question 24

diamond usage

Answer 24

cutting tools, jewelery

Question 25

graphite usage

Answer 25

pencils, lubricants, electrodes

Question 26

structure of silicon (IV) oxide

Answer 26

tetrahedral macromolecular structure similar to diamond - each Silicon atom is covalently bonded with 4 oxygen atoms - high m.p and b.p - rigid and hard - non conductor of electricity

Question 27

similarities of diamond and silicon oxide

Answer 27

- hard, rigid, 3D structures - tetrahedral crystals - non-conductors of electricity - high m.p and b.p

Question 28

why does silicon oxide have a high melting point

Answer 28

SiO is a macromolecular structure that consists of an extensive network of strong covalent bonds. A large amount of energy is needed to break some of these bonds in order to melt it, hence high melting point

Question 29

metallic bonding

Answer 29

electrostatic attraction between the positive ions in a metallic lattic and a sea of delocalised electron