Elements of Life

Question 1

How do we weigh atoms?

Answer 1

We weigh atoms by mass spectrometry

Question 2

What is mass spectrometry?

Answer 2

Mass spectrometry is an accurate way to measure (instrumental technique) used to find the relative abundance and relative mass of an isotope.

Question 3

How does mass spectrometry work?

Answer 3

Ionisation - An electron gun removes electrons from the sample material (positive ions)
Acceleration - Ions are attracted to negatively charged plates (opposites attract)
Deflection - The direction of ions is changed by an electromagnetic field
Detection - Ions strike a counter plate which causes a current to flow, this is then recorded on a computer

Question 4

What does mass spectrometry tell us?

Answer 4

The mass spectrometry graphs peaks tells us the atomic mass in the form of mass:charge ratio (usually called the M/Z value).
The peak intensity gives the relative abundance
The highest abundance is scaled up to 100% and the other values are adjusted accordingly.

Question 5

Empirical formula

Answer 5

Empirical formula is the simplest ratio of atoms in a compound

Question 6

Molecular formula

Answer 6

The actual number of each atom in a compound

Question 7

Spectrometry

Answer 7

Under certain conditions a substance can either emit or absorb EM radiation and spectrometry is the study of how light and matter interact.

As frequency increases the energy also increases, but wavelength decreases.

Question 8

Absorption Spectrometry

Answer 8

In absorption spectrometry atoms absorb EM radiation (energy). This promotes an electron in the shell of an atom to be promoted from its ground state to a much higher excited rate with an increased amount of energy. This results in black absorption lines in a coloured spectrum (these lines are where frequencies of light have been absorbed by the atom.

Question 9

Emission Spectrometry

Answer 9

In order to lose the extra energy produced from absorbing energy (EM radiation), the electron falls back to its ground state - this emits light energy. This results in a black spectra covered with coloured emission lines of emitted light from the atom.

Question 10

Spectrometry of stars in space

Answer 10

white light contains all the visible wavelengths and its spectra is continuous. The light from stars is non-continous - it consists of lines, corresponding to the absorption or emission of specific frequencies of light.

Question 11

Spectrometry for specific elements (Bohr’s energy levels)

Answer 11

Each element shows specific absorption and emission lines which are specific to the atom of that element.

His theory was:
Electrons exist in certain discreet energy levels.
A photon of light is emitted/absorbed when an electron changes from one energy level to another.
The photon energy is the energy difference - and therefore only certain frequencies are emitted/absorbed so they’re not continuous.

Question 12

Flame Tests

Answer 12

When metal compounds are placed in a bunsen burner flame, the electrons in the metal atoms absorb energy from the flame and are promoted to higher (excited) energy levels. The electrons then emit energy as they fall back to their lower energy levels.

Question 13

FLAME TEST - LITHIUM

Answer 13

BRIGHT RED

Question 14

FLAME TEST - SODIUM

Answer 14

YELLOW

Question 15

FLAME TEST - POTASSIUM

Answer 15

LILAC

Question 16

FLAME TEST - BARIUM

Answer 16

APPLE GREEN

Question 17

FLAME TEST - CALCIUM

Answer 17

BRICK RED

Question 18

FLAME TEST - COPPER

Answer 18

BLUE/GREEN

Question 19

Electron Configurations

Answer 19

Each energy shell is designated a principle quantum number (N), the higher the value of ‘N’ the greater the energy and we fill up from the lowest energy levels.

Question 20

ELECTRON SHELL

Answer 20

An electron shell is the amount of energy as designated by the principle quantum number

Question 21

SUBSHELL

Answer 21

A subshell is a sub division of an electron shell

Question 22

ATOMIC ORBITAL

Answer 22

An atomic orbital is a further divided orbital

Question 23

ORBITAL

Answer 23

An orbital is a region in space where one is likely to find an electron, electrons can only occupy the same orbital if they have opposite or paired spins. EACH ORBITAL CAN HOLD UP TO TWO ELECTRONS AS LONG AS THEY HAVE OPPOSITE SPIN

Question 24

ORBITAL ELECTRON SPIN

Answer 24

Electrons in an atom have a spin (in one of two directions), every electron spins at the same rate in either a clockwise of anti-clockwise direction.

Question 25

HOW ELECTRON’S ARE FILLED

Answer 25

1S, 2S, 2P, 3S, 3P, 4S, 3D, 4P, 4D, 4F, 5S, 5P, 5D, 5F, 6S, 6P, 6D, 7S, 7P

Question 26

what were Hunds rules?

Answer 26

Every orbital in a sublevel is singly occupied before any orbital is doubly occupied .
All of the electrons in a singly occupied orbital have the same spin.
Orbitals are filled according to HUND’S LAW

Question 27

AUFBAU PRINCIPLE

Answer 27

Electrons orbiting one or more atoms fill the lowest available energy levels before filling the highest energy levels.

Question 28

ATOMIC RADIUS

Answer 28

The non-bonded atomic radius of an atom is half of the distance between two unbounded atoms of the same element when the electrostatic forces are unbalanced.

As you move along a period, the proton number increases and this means that the atomic radius decreases, this is because the electrostatic force between the outer electrons and nucleus increases.

Question 29

FIRST IONISATION ENERGY

Answer 29

The first ionisation energy of an atom is the minimum energy required to remove an electron from a neutral atom in its ground state.

As protons increase, the atoms get smaller and therefore there’s a stronger attraction from the nucleus to the electrons in the outer shell.

EXAM DEFINITION - The first ionisation energy is the energy needed to remove one electron from one mole of gaseous atoms to form one mole of gaseous 1+ ions.

Question 30

ELECTRONEGATIVITY

Answer 30

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
As you go from the bottom left corner of the PT to the top right corner the electronegativity increases - this means its easier for the the nucleus to attract electrons, more easily creating covalent bonds. ‘THE ABILITY OF AN ATOM TO ATTRACT THE ELECTRON PAIR IN A COVALENT BOND TO ITSELF’.

Question 31

ELECTRON SHEILDING

Answer 31

The more shells there are, the greater the shielding so the outer electrons feel less of the positive protons attraction.

Question 32

CHEMICAL BOND

Answer 32

A chemical bond is a strong force of electrical attraction (electrostatic attraction) between atoms and or ions in a structure. It involves the sharing or transferring of electrons in the highest occupied electron shells (the most stable arrangement of electrons).

Question 33

COVALENT BOND

Answer 33

Electrostatic attraction of two atoms due to a pair of electrons being shared

Question 34

MULTIPLE BOND

Answer 34

More than 2 pairs of electrons being shared

Question 35

DIFFERENT SHAPES

Answer 35

LEWIS STRUCTURE - Dot and cross diagram
STRUCTURAL FORMULA - Drawn as a single line
COORDINATE/DATIVE BOND - Shared pair of electrons, both being supplied by one atom - drawn as an arrow.

Question 36

VSEPR (Valance shell Electron Pair Repulsion Theory)

Answer 36

Molecules contain covalent bonds and because covalent bonds consist of pairs of electrons, each bond will repel other bonds. When bonds are closer together the repulsive forces are greater and when bonds are further apart/equal distance apart then the repulsive forces are less. Bonds will therefore push each other as far apart as possible in order to reduce the repulsive forces and when repulsions are equal the bonds are equally spaced apart.

“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR ION IS THAT WHICH KEEPS REPULSIVE FORCES TO A MINIMUM”

Question 37

LONE PAIRS

Answer 37

If a molecule/ion has lone pairs in the CENTRAL ATOM then the shapes are slightly distorted away from the regular shape - this is because of the extra repulsion caused by lone pairs.

Question 38

ELECTRON CONFIGURATION

Answer 38

The arrangement of electrons in shells and orbitals

Question 39

explain how the spectrum for each element is unique

Answer 39

each element has a different electron arrangement, so the frequencies of radiation absorbed and emitted are different, this means the spectrum for each element is unique.