Elements of Life

Question 1

Isotope

Answer 1

Atoms of the same element (thus containing the same number of protons) with a different number of neutrons

Question 2

Nuclear fission

Answer 2

A large nucleus (such as the Lanthanides and Actinides) splits into smaller nuclei, e.g. fission process used in nuclear power plants

Question 3

Nuclear fusion

Answer 3

Smaller nuclei (such as hydrogen and helium) fuse to form a larger nucleus, e.g. creation of elements in stars

Question 4

Alpha (α) radiation

Answer 4

A strongly ionising helium nucleus (2+ charge) with a short range (a few centimetres in air) in air. Very little deflection by a magnetic field; stopped by a sheet of paper

Question 5

Beta (ß) radiation

Answer 5

Weakly ionising electrons (1- charge) emitted from the nucleus when a neutron decays into a proton and an electron. Travel a few metres in air; high deflection by a magnetic field; stopped by aluminium foil

Question 6

Gamma (Ɣ)

Answer 6

Non-ionising electromagnetic radiation with a very long range in air. Not deflected by a magnetic field; stopped by a sheet of lead or several metres of concrete

Question 7

α particle

Answer 7

4/2 He

Question 8

ß particle

Answer 8

0/-1 e

Question 9

Ɣ particle

Answer 9

Photons of high frequency electromagnetic radiation

Question 10

Hydrogen fusion

Answer 10

The means by which stars release energy; in the early universe “clouds” of hydrogen nuclei fused together under a high temperature and pressure to form stars; continued fusion formed the “light” elements (up to iron). Heavier elements were formed in supernovae under conditions of huge temperature and pressure

Question 11

Absorption and emission spectra

Answer 11

Under certain conditions elements emit or absorb electromagnetic radiation in a characteristic way. Absorption spectra appear as black lines on a bright background, while emission spectra are the inverse of this

Question 12

Balmer series

Answer 12

A diagram showing how outermost electrons can be excited to unstable higher levels, only to emit photons to get back to ground level

Question 13

Star structure

Answer 13

The photosphere, the glowing surface of a star that emits visible light, is surrounded by atoms and ions that absorb light from the photosphere, producing absorption spectra. The corona, an area of high temperature surrounds the star and contains ions such as Mg 11+ and Fe 15+

Question 14

Light emission

Answer 14

The outermost electrons of an atom start in a stable “ground state”, and when heat, light or energy is applied the molecules transition into a higher, unstable state. When the electron goes back to ground state it emits energy as a photon of light or electromagnetic radiation

Question 15

Wave-particle duality

Answer 15

Light can be imagined with two models: as a wave, equation c = f ƛ; and as a particle, equation E = h f. The energy of the light is a function of it’s wavelength, E = c h / ƛ

Question 16

Bohr’s Theory

Answer 16

Atomic spectra are caused by electrons in atoms moving between different energy levels (shells and sub-shells)

Question 17

Electron shells

Answer 17

Electrons are arranged in principal energy levels which contain overlapping sub shells

Question 18

Electron sub-shells

Answer 18

S-orbital contains one orbital with two electrons; P-orbital contains three orbitals with six electrons; D-orbital contains five orbitals with ten electrons

Question 19

Sub-shell order

Answer 19

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10

Question 20

Electron configuration rules

Answer 20

The lowest energy sub-levels are occupied first (the Aufbau principle); single electrons fill empty orbitals before forming pairs (Hund’s rule); each orbital contains a maximum of two electrons (the Pauli exclusion principle)

Question 21

Dative covalent bonds

Answer 21

In a dative covalent bond, one atom contributes both electrons to the covalent bond. The bond line is replaced by an arrow, demonstrating where the electrons come from

Question 22

Electron Pair Repulsion theory

Answer 22

Areas of electron density repel each other as they are negatively charged, so they move as far apart as possible to reduce the repulsions