1.2 Basic ideas about atoms Flashcards

Question

Write an equation for beta decay.

Answer 1

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

Answer 2

The greater the half-life of a radioactive isotope, the greater the concern since the radioactivity of the isotope exists for a longer time.

Answer 3

Ionising radiation may damage the DNA of a cell. Damage to the DNA may lead to changes in the way the cell functions, which can cause mutations and the formation of cancerous cells at lower doses or cell death at higher doses.

Answer 4

Cobalt-60 in radiotherapy for the treatment of cancer. The high energy of gamma radiation is used to kill cancer cells and prevent a malignant tumour from developing. Radioactive isotopes are also used as tracers to label a molecule which is preferentially taken up by the tissue to be studied.

Answer 5

1. Measuring thickness of metal strips of foil 2. Dilution analysis

Answer 6

A region in an atom that can hold up to two electrons with opposite spins.

Answer 7

2 electrons

Answer 8

6 electrons

Answer 9

10 electrons

Answer 10

14 electrons

Answer 11

1. Electrons fill atomic orbitals in order of increasing energy 2. A maximum of 2 electrons can occupy each orbital each with opposite spins 3. The orbitals will first fill with one electron each with parallel spins, before a second electron is added with the paired spin.

Answer 12

The arrangement of electrons in an atom

Answer 13

1s² 2s² 2p⁶ 3s² 3p⁴ 3d⁵ 4s¹

Answer 14

1s2 2s2 2p6 3s2 3p6 4s1 3d10

Answer 15

The process of removing electrons from an atom

Answer 16

The energy required to remove one electron from each atom in one mole of its gaseous atoms

Answer 17

X(g) ----> X+ (g) + e-

Answer 18

Electrons are held in their shells by their attraction to the positive nucleus, therefore, the greater the attraction, the greater the ionisation energy. This depends on the factors: 1. The size of the positive nuclear charge - the greater the nuclear charge, the greater the attractive force on the outer electrons, so greater the ionisation energy 2. The distance of the outer electron from the nucleus - force of attraction between nucleus and outer electron decreases as the distance increases. The further the outer electron is from the nucleus, the lower the ionisation energy 3. The shielding effect by electrons in filled inner shells - all electrons repel each other since they are negatively charged. Electrons in the filled inner shells repel electrons in the outer shell and reduce the effect of the positive nuclear charge. The more filled inner shells, the smaller the attractive force in the outer electron and lower the ionisation energy.

Answer 19

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

Answer 20

Helium has greater nuclear charge in the same subshell so little extra shielding.

Answer 21

Lithium's outer electron is in new shell, which has increased shielding and is further away from nucleus

Answer 22

Boron's outer electron is in a new subshell of slightly higher energy level and is partly shielded by the 2s electrons

Answer 23

electron-electron repulsion between two paired electrons in one p-orbital in oxygen makes one of the electrons easy to remove. nitrogen does not have any paired electrons in p-orbital

Answer 24

neon's outer electron has increased shielding from inner electrons and is further from the nucleus.

Answer 25

A measure of the energy needed to remove each electron in turn until all the electrons are removed from an atom

Answer 26

Because: 1. There is a greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons. 2. As each electron is removed, there is less electron-electron repulsion and each shell will be drawn slightly closer to the nucleus. 3. As the distance of each electron from the nucleus decreases, the nuclear attraction increases.

Answer 27

E = hc/λ h = Planck's constant c = speed of light

Answer 28

When white light is passed through the vapour of an element, certain wavelengths will be absorbed by the atoms and removed from the light. Black lines appear in the spectrum where light of some wavelengths has been absorbed. Wavelengths of these lines correspond to the energy taken in by the atoms to promote electrons from lower to higher energy levels

Answer 29

When the source of energy is removed and the electrons leave the excited state, they fall from the higher energy level to a lower energy level and the energy lost is released as a photon with a specific frequency. The observed spectrum consists of a number of coloured lines on a black background. The fact that only certain colours appear in an atom's emission spectrum means that only photons having certain energies are emitted by the atom.

Answer 30

When an atom is excited by absorbing energy, an electron jumps up to a higher energy level. As the electron falls back down to a lower energy level, it emits energy in the form of electromagnetic radiation. The emitted energy can be seen as a line in the spectrum because the energy of the emitted radiation is equal to the difference between the two energy levels (i.e. it is quantised)

Answer 31

electrons returning to the first shell (ultraviolet region)

Answer 32

electrons returning to the second shell (visible region)

Answer 33

The point at which the energy of an electron is no longer quantised. AT that point the nucleus has lost all influence over the electron; the atom has become ionised. For the Lyman series, the convergence limit represents the ionisation of the hydrogen atom. Measuring the convergent frequency allows the ionisation energy to be calculated using E=hf. The value of E is multiplied by avogadro's constant to give the first ionisation energy for a mole of atoms.