Topic 1- Elements Of Life

Question 1

What is the relative mass, charge and location of a neutron?

Answer 1

Relative mass= 1
Charge= 0
Location= nucleus

Question 2

What is the relative mass, charge and location of an electron?

Answer 2

Relative mass= 0.00055
Charge= -1
Location= energy levels around the nucleus

Question 3

What is the relative mass, charge and location of a proton?

Answer 3

Relative mass= 1
Charge= +1
Location= nucleus

Question 4

What are the atomic number and the mass number of an element?

Answer 4

Atomic number= the number of protons (and electrons)

Mass number= the number of protons and neutrons

Question 5

What is an isotope?

Answer 5

Atoms of the same element that have the same atomic number (proton number) but different mass numbers (numbers of neutrons)

Question 6

How can you work out the relative mass of an element from all of its isotopes?

Answer 6

                     100

Question 7

What does radioactive mean?

Answer 7

When the nucleus of an atom is unstable and breaks down (decays) randomly emitting radiation. (Either alpha, beta or gamma)

Question 8

What is alpha decay?

Answer 8

A helium nucleus (2 protons and 2 neutrons)
Range in air: few cm
Stopped by: paper
Deflection by an electrical field: low

Question 9

What is beta decay?

Answer 9

An electron, a neutron is converted into a proton and a electron, the electron is ejected from the nucleus.
Range in air: a few m
Stopped by: aluminium foil
Deflection by electrical field: high

Question 10

What is gamma decay?

Answer 10

An imparticulate high frequency electromagnetic wave.

Range in air: very long
Stopped by: lead sheet
Deflection by electrical field: nil

Question 11

What is nuclear fusion?

Answer 11

2 light atomic nuclei fuse together to form a single heavier nucleus of a new element. This releases large quantities of energy.
Large amounts of energy are needed because at normal temperatures the 2 positive nuclei repel at high temperatures nuclei move with more energy and so collide with enough energy to overcome the energy barrier

Question 12

What is half life?

Answer 12

The time taken for half of a radioactive nuclei to decay.

Question 13

How can you use radioisotopes in geology?

Answer 13

Geological clocks- if the original isotope decays to eventually form a stable daughter product then measuring the ratio of parent:daughter we can predict the age of the rock.

Question 14

What criteria must be filled to predict the age of a rock using radioisotopes?

Answer 14

• half life of the radioisotope must be known accurately
• there must have been no movement of parent/daughter into/out of the rock
• must be no ‘resetting’ of the radioactive clock e.g. Melting and reforming

Question 15

How can radioisotopes be used to date archeological remains?

Answer 15

The ratio of C12 to C14, when an organism dies the ratio of C12 to C14 gradually increases. This makes it useful for dating remains up to about 50,000 years old. Beyond this the amount of C14 remaining is so small that measurements become difficult

Question 16

What are radioactive tracers used for? What should be their properties?

Answer 16

Radioactive isotopes can be injected into the body to locate problems e.g. Cancerous tumours.
They should be gamma emitters- to enable detection and minimise ionisation of cells.
They should have a short half life to allow detection but minimise harm to the patient

Question 17

Why do all atoms react to gain a full outer shell?

Answer 17

Because this is the most stable and low energy arrangement.

Question 18

What is ionic bonding?

Answer 18

When electrons are transferred from metal atoms to non-metal atoms to create 2 charged particles, or ions. This charge radiates over the entire surface of the ions and so a 3-D arrangement called a lattice is formed.

Question 19

What is covalent bonding?

Answer 19

Electrons are shared as outer energy levels overlap.
As 2 atoms approach there is a shared attraction by the nuclei for the pair of electrons. However there will also be a force of repulsion as the 2 nuclei get so close they repel. The bond is made when there is an overall distance where attraction= repulsion.

Question 20

What is dative covalent bonding?

Answer 20

When the bonding pair of electrons comes from only one of the atoms, it is represented by an arrow.

Question 21

What is the atomic core of an atom?

Answer 21

Nucleus + inner full shells. The atomic core is the charge that you are left with. From group 1-7 the atomic core increases from +1 to +7
The atomic core shows the ‘power’ of an atom to attract a pair of electrons in a bond

Question 22

What is electronegativity?

Answer 22

When an atom has the ability, because of its nucleus radiating positive charge, to attract incoming electrons we say it is electronegative.

Question 23

What causes an atom to be more electronegative?

Answer 23

• if it is smaller (fewer shells) shielding the nucleus

- if it has a more positive atomic core

Question 24

What are the most electronegative elements?

Answer 24

Most electronegative= fluorine

F, O, N, Cl

Question 25

What is a polar covalent bond?

Answer 25

When an element that is more electronegative bonds with an element less electronegative covalently and attracts the bonding pair of electrons closer to itself giving it a d- charge and the other a d+ charge.

Question 26

What is metallic bonding?

Answer 26

The outer electrons are lost from the metal atoms, leaving positive ions in a sea of delocalised electrons. Metals are solid at room temperature because an electrostatic attraction exists between the ions and electrons. This requires large amounts of energy to overcome.

Question 27

What is the electron pair repulsion theory?

Answer 27

The electrons around the outer shell exist in pairs and these pairs of electrons repel each other so that they are as far apart from each other as possible.

Question 28

What shape and bond angle do 2 electron pairs create?

Answer 28

A linear shape with a bond angle of 180 degrees.

Question 29

What shape and bond angle do 3 pairs of electrons create?

Answer 29

A trigonal planar shape is created with a bond angle of 120 degrees.

Question 30

What shape and bond angle do 4 pairs of bonding electrons create?

Answer 30

A tetrahedral shape is created with a bond angle of 109 degrees

Question 31

What shape and bond angle do 3 bonding pairs and 1 lone pair of electrons create?

Answer 31

Trigonal pyramidal shape is created with a bond angle of 109 (107) degrees

Question 32

What shape and bond angle do 2 bonding pairs and 2 lone pairs of electrons create?

Answer 32

A bent shape is created, which a bond angle of 109 (104.5) degrees.

Question 33

What shape and bond angles do 5 bonding pairs of electrons create?

Answer 33

A trigonal bipyramidal shape is created with a bond angle of 90 degrees (@the top) and 120 degrees (@the bottom)

Question 34

What shape and bond angle do 6 bonding electron pairs create?

Answer 34

An octahedral shape with a bond angle of 90 degrees is created.

Question 35

What is the mole concept?

Answer 35

Number of moles= mass of substance ----------------------- Ar/Mr 1 mole= 6.02 x 10^23

Question 36

What are the 2 theories of light?

Answer 36

1. Wave theory- treats light as one continuous wave c= f x wavelength 2. Particle theory- treats light as a particle- photons. E= h x f

Question 37

What is an emission spectrum?

Answer 37

When a sample of a substance is given energy the electrons become excited as they absorb energy and move out of ground state. After a period of time the electrons 'lose' this energy and EMIT it to the surroundings, this emitted energy can be detected and create an emission spectrum which can be observed as a series of lines.

Question 38

Why does each element have a different emission spectrum?

Answer 38

Every element will absorb and re-emit different energies and therefore different frequencies of em waves and so we will see different lines. This makes it possible to identify atoms in different EM emitting sources e.g stars

Question 39

What is the difference between emission and absorption spectrums?

Answer 39

Emission spectrum is a series of coloured lines on a black background, this shows only frequencies of radiation emitted by an atom Absorption spectrum is a series of black lines on a coloured background so you see the frequencies of radiation the element has absorbed

Question 40

What is periodicity?

Answer 40

When similarities in trends in properties are seen as you go across a period.

Question 41

Give an equation for the reaction of a group 2 element with water

Answer 41

M(s) + H2O ----> M(OH)2 (aq) + H2 (g) The reactivity increases as you go down group 2

Question 42

Give an equation for heating a group 2 metal carbonate.

Answer 42

MCO3(s) ----> MO(s) + CO2(g) They become more difficult to decompose as you go down the group, thermal stability increases.

Question 43

What are the solubilities of compounds of group 2 metals?

Answer 43

Hydroxides, as you go down the group the solubility increases Carbonates, as you go down the group the solubility decreases