Chapter 2 Atoms, ions and compounds

Question 1

Isotopes

Answer 1

• Same number of protons and electrons
• Atoms of the same element with different number of neutrons and different masses
• Most elements are made up of a mixture of isotopes

Question 2

Atomic structure

Answer 2

• Protons
• Neutrons
• Electrons

Question 3

Mass of protons, neutrons and electrons

Answer 3

• Protons and neutrons have the same relative mass of 1
• Electrons have a negligible mass

Question 4

Overall charge of an atom

Answer 4

The charges of the protons and electrons cancel out -> atom is neutral (no overall charge)

Question 5

Ratio of number of protons: number of neutrons in an atom

Answer 5

same

Question 6

Atomic number

Answer 6

Number of protons

Question 7

Mass number

Answer 7

Number of protons + number of neutrons

Question 8

Isotopes and chemical reactions

Answer 8

• Different isotopes of the same element have the same number of electrons
• Number of neutrons has no effect on reactions of an element -> different isotopes of an element react in the same way

Question 9

Isotopes and physical reactions

Answer 9

Higher mass isotopes of an element have a higher melting point, boiling point and density

Question 10

Ion

Answer 10

• Charged atom
• Number of electrons is different from the number of protons

Question 11

Cations

Answer 11

• Positive ions
• Less electrons than protons

Question 12

Anions

Answer 12

• Negative ions
• More electrons than protons

Question 13

What predicts chemical reactions

Answer 13

Number of electrons

Question 14

Mass of a carbon-12 isotope

Answer 14

12 atomic mass units (12u)

Question 15

The standard mass for atomic mass

Answer 15

1u, the mass of 1/12th of an atom of carbon-12

• 1u = mass of a proton or a neutron

Question 16

Relative isotopic mass

Answer 16

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

Question 17

Relative atomi mass (Ar)

Answer 17

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

Question 18

The weighted mean mass takes account of:

Answer 18

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

Question 19

Mass spectrometer

Answer 19

to find % abundance of the isotopes in a sample of an element experimentally

Question 20

Process of a mass spectrometer

Answer 20

1. A sample is placed in the mass spectrometer
2. The sample is vaporised
3. The sample is ionised (to give each particle a positive charge)
4. Ions are accelerated
5. Ions are deflected (size of deflection depends on the mass so heavier isotopes are deflected less than lighter ones)
6. The ions are detected as an m/z
7. Each ion reaching the detector adds to the signal, so the greater the abundance, the larger the signal

Question 21

m/z full form

Answer 21

mass:charge ratio

Question 22

Equation of m/z

Answer 22

m = relative mass of ion
z = relative charge on ion

Question 23

Axis on the graph of m/z

Answer 23

x-axis: m/z
y-axis: % abundance

Question 24

Binary compounds

Answer 24

Contains 2 elements only

Question 25

Binary compounds

Answer 25

• Name of 1st element + add -ide to second element
• for ionic compounds, metal ion comes first

Question 26

Polyatomic ions

Answer 26

An ion contain atoms of more than one element bonded together

Question 27

Writing formulae from ions

Answer 27

• The overall charge is zero so the ionic charges must balance
• sum of positive charges = sum of negative charges

Question 28

Diatomic molecules

Answer 28

contain 2 atoms bonded together

Question 29

State symbols

Answer 29

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

Question 30

Do ions have the same mass number or different mass number?

Answer 30

Same mass number