Chapter 2 - Atoms, Ions and Compounds

Question 1

what does an atom consist of?

Answer 1

• the nucleus: made up of protons and neutrons
• electrons arranged around the nucleus in shells

Question 2

what are the relative masses of protons, neutrons and electrons?

Answer 2

proton: 1
neutron: 1
electron: negligable

Question 3

what are the relative charges of protons, neutrons and electrons?

Answer 3

proton: +1
neutron: 0
electron: -1

Question 4

where is an atoms mass?

Answer 4

nearly all of an atoms mass is in the nucleus

Question 5

what is an atoms charge?

Answer 5

atoms have a charge of 0 as they have the same number of protons as electrons so the charges cancel

Question 6

what is atomic number?

Answer 6

the number of protons in an atom. every atom of the same element contains the same number of protons.

Question 7

what is an isotope?

Answer 7

atoms of the same element with different numbers of neutrons and therefore different masses

Question 8

what is the symbol and definition of mass number?

Answer 8

symbol: A
definition: total number of protons + total number of neutrons

Question 9

what is the symbol and definition of atomic number?

Answer 9

symbol: Z
definition: total number of protons

Question 10

do different isotopes of an element react in the same way?

Answer 10

• chemical reactions involve the electrons surrounding the nucleus
• different isotopes of the same element have the same number of electrons
• the number of neutrons has no effect on reactions of an element

Question 11

what is a cation?

Answer 11

a positive ion, an atom with less electrons than protons so has an overall positive charge

Question 12

what is a anion?

Answer 12

a negative ion, an atom with more electrons than protons so has an overall negative charge

Question 13

what is one atomic mass unit (1 u)?

Answer 13

1/12th of an atom of carbon-12 and approximately the mass of a proton or neutron

Question 14

what is the definition of relative isotopic mass?

Answer 14

the mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Question 15

what can you assume relative isotopic mass is the same as?

Answer 15

the mass number A of the isotope

Question 16

what is relative atomic mass?

Answer 16

the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 17

what does weighted mean mass take account of?

Answer 17

• the percentage abundance of each isotope
• the relative isotopic mass of each isotope

Question 18

how can you find the percentage abundances of the isotopes in a sample of an element?

Answer 18

using a mass spectrometer

Question 19

how do mass spectrometers work?

Answer 19

• a sample is placed in the mass spectrometer
• the sample is vaporised and then ionised to form positive ions
• the ions are accelerated. heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each element are separated
• the ions are detected on a mass spectrum as a mass-to-charge ration m/z. this is roughly equivalent to the relative isotopic mass

Question 20

which side of the periodic table form cations?

Answer 20

the left

Question 21

which side of the periodic table form anions?

Answer 21

the right

Question 22

what happens when elements can form several ions with different charges?

Answer 22

the ionic charge is shown with a roman numeral in the name of the ion e.g. iron (III)

Question 23

what is a binary compound?

Answer 23

a compound that contains two elements only

Question 24

how do you name a binary compound?

Answer 24

use the name of the first element but change the ending of the second elements name to -ide
for ionic compounds, the metal ion always comes first

Question 25

what is the charge on ammonium (NH4)?

Answer 25

1+

Question 26

what is the charge on hydroxide (OH)?

Answer 26

1-

Question 27

what is the charge on nitrate(NO3)?

Answer 27

1-

Question 28

what is the charge on nitrite(NO2)?

Answer 28

1-

Question 29

what is the charge on hydrogencarbonate(HCO3)?

Answer 29

1-

Question 30

what is the charge on manganate(VII)/permanganate(MnO4)?

Answer 30

1-

Question 31

what is the charge on carbonate(CO3)?

Answer 31

2-

Question 32

what is the charge on sulphate(SO4)?

Answer 32

2-

Question 33

what is the charge on sulphite(SO3)?

Answer 33

2-

Question 34

what is the charge on dichromate(VI)(Cr2O7)?

Answer 34

2-

Question 35

what is the charge on phosphate(PO4)?

Answer 35

3-

Question 36

how do you write the formula of an ionic compond?

Answer 36

balance the charges so the overall charge is zero

Question 37

what elements are seen as molecules?

Answer 37

H2, N2, O2, F2, Cl2, Br2, I2, P4 and S8 (Sulphur is written as S for equations)

Question 38

how are elements shown in equations?

Answer 38

just as their symbol (apart from elements seen as molecules)

Question 39

what are the state symbols?

Answer 39

(g) - gas (l) - liquid (s) - solid (aq) - dissolved in water (aqueous)

Question 40

what are the rules of balancing equations?

Answer 40

- you must not change any chemical formula - balancing numbers go in front of chemical formula and aren't written as subscript - the equation is balanced when there are the same number of atoms of each element on each side of the equation

Question 41

what happens when you have to balance formulae with brackets?

Answer 41

the balancing number multiplies anything within the bracket