Basic ideas about atoms

Question 1

What is the atomic number?

Answer 1

The number of protons in the nucleus of an atom.

Question 2

What is the mass number?

Answer 2

The number of protons and neutrons in the nucleus of an atom.

Question 3

What are isotopes?

Answer 3

Atoms with the same number of protons but a different number of neutrons.

Question 4

How are positive ions (cations) formed?

Answer 4

When an atom loses one or more electrons.

Question 5

How are negative ions (anions) formed?

Answer 5

When an atom gains one or more electrons.

Question 6

What is alpha radiation and its properties?

Answer 6

A helium nucleus, least penetrating (stopped by air), most ionising.

Question 7

What is beta radiation and its properties?

Answer 7

High energy electron, stopped by a thin layer of metal.

Question 8

What is positron radiation and its properties?

Answer 8

Anti electron, stopped by a thin layer of metal.

Question 9

What is gamma radiation and its properties?

Answer 9

Electromagnetic wave, most penetrating (stopped by lead), least ionising.

Question 10

What is the half life?

Answer 10

The time taken for half the atoms in a radioisotope to decay.

Question 11

When an element emits alpha radiation, what happens to its mass and atomic number?

Answer 11

Its mass number decreases by 4 and its atomic number decreases by 2.

Question 12

When an element emits beta radiation, what happens to its mass and atomic number?

Answer 12

Its mass number is unchanged and its atomic number increases by 1.

Question 13

When an element emits positron radiation, what happens to its mass and atomic number?

Answer 13

Its mass number is unchanged and its atomic number decreases by 1.

Question 14

What are the dangers of high energy radioactive emission?

Answer 14

They break chemical bonds in cell molecules, giving rise to changes in DNA which can cause mutations and the formation of cancerous cells at low doses, and cell death at high doses.

Question 15

What are some beneficial uses to radioactivity?

Answer 15

In Medicine: Colbalt-60 used in radiotherapy to treat cancer
In Radio-dating: Carbon-14 used to calculate the age of plant and animal remains
In Analysis: Monitoring the thickness of foil

Question 16

What shape is the S orbital?

Answer 16

Spherical and contains up to two electrons.

Question 17

What shape is the P orbital?

Answer 17

Dumbbell and contains up to six electrons.

Question 18

What shape is the D orbital?

Answer 18

Dumbbell with a ring and contains up to ten electrons.

Question 19

What is electron configuration?

Answer 19

The arrangements of electrons in an atom.

Question 20

What is electron shielding?

Answer 20

The repulsion between electrons in different shells. Inner shell electrons repel outer shell electrons.

Question 21

Nuclear attraction depends on what factors?

Answer 21

Nuclear charge
Electron shielding
Distance of the outer electron to the nucleus

Question 22

What is the first molar ionisation energy?

Answer 22

The energy to remove one mole of electrons from one mole of gaseous ions to form one mole of 1+ gaseous ions.

Question 23

Why do successive ionisation energies always increase?

Answer 23

There is a greater nuclear charge as the same number of protons are holding fewer electrons
As each electron is removed there is less repulsion and each shell is drawn slightly closer to the nucleus
As the distance of each electron from the nucleus decreases, the nuclear attraction increases

Question 24

Describe the steps of the emission spectrum

Answer 24

*Electron absorbs energy and jumps to higher level
*Electron is excited and drops to a lower energy level
*Emits a photon in the visible region corresponding to the gap in energy levels

Question 25

What is in the Paschen series?

Answer 25

Infrared light (n=3).

Question 26

What is in the Balmer series?

Answer 26

Visible light (n=2).

Question 27

What is in the Lyman series?

Answer 27

Ultraviolet light (n=1).

Question 28

What is the convergence limit?

Answer 28

When the spectral lines become so close together they have a continuous band of radiation and separate lines can’t be distinguished.

Question 29

Describe the steps of the absorption spectrum

Answer 29

When white light is passed through the vapour of an element, certain wavelengths will be absorbed by the atoms, and removed from the light. The wavelength of the lines correspond to the energy taken in by the atoms to promote electrons from lower to higher energy levels.

Question 30

How to find energy?

Answer 30

Energy= plancks constant x speed of light/ wavelength

Question 31

What is the emission spectrum for a hydrogen atom?

Answer 31

A line upwards from n=1 to n=infinity.

Question 32

State the regions of light in the emission spectrum in increasing energies

Answer 32

Infrared -> Visible -> Ultraviolet

Question 33

How can you use the emission spectrum to calculate ionisation energy?

Answer 33

By measuring the wavelength at the convergence limit and using E=hf or E=hc/wavelength to calculate energy.

Question 34

What are there several series of lines?

Answer 34

Each line corresponds to electron falling to different energy levels.

Question 35

Why do the lines of each series converge?

Answer 35

As energy levels get closer together.