Electron arrangement and the Periodic Table

Question 1

3 Subatomic particles + Charges

Answer 1

1. Protons ( positively charged )
2. Neutrons ( negatively charged )
3. Electron ( no charge )

Question 2

Nucleus

Answer 2

small, dense protons and neutrons

Question 3

Electron cloud

Answer 3

region of space where the is a probability of an electron being found

Question 4

Emission spectrum and the Atom

Answer 4

• As an element is heated, electrons absorb energy
  and can be promoted to a higher energy state known
  as the exited state.
• Shortly afterwords, the electron ‘relapses’ to the lower
  energy state, known as the ground state, releasing a
  fixed amount of energy (a photon) as electromagnetic
  radiation (eg. light).
• Electrons can return via a number of different
  pathways, each one producing its own particular
  wavelength in the emission spectrum.

Question 5

What is needed for an electron to be promoted to a higher electron shell?

Answer 5

An input of energy

Question 6

What happens when an excited electron relapses into the ground state?

Answer 6

A photon of energy is released as electromagnetic radiation

Question 7

What name is given to the sublevel of electron organisation within each shell?

Answer 7

A subshell

Question 8

Electron Shell

Answer 8

An energy level within an atom that may be occupied by a fixed number of electrons

Question 9

Subshell

Answer 9

A subdivision of an electron shell, containing a fixed number of orbitals at the same energy level

Question 10

Orbital

Answer 10

A region of space in which up to two electrons may be located

Question 11

The Aufbau Principle

Answer 11

• Electrons move into sub-shells in order from lowest energy to highest energy

Question 12

Hund’s Rule

Answer 12

All orbitals in a sub-shell will be half‐filled before any are filled completely (maximising the number of half‐filled orbitals)

Question 13

The Pauli Exclusion Principle

Answer 13

maximum of two electrons may occupy any given atomic orbital, provided that they have opposite spin

Question 14

sub-shell electronic configuration of ions

Answer 14

Transition metal atoms in period 4 lose their 4s electrons before their 3d electrons.

Question 15

Core Charge

Answer 15

Measure of the net attractive force felt by the valence shell electrons towards the nucleus

Number of protons - number of electrons in in a shell every electron besides valence

Call charge = group number

Question 16

Atomic Radius

Answer 16

Half the distance between two nuclei of a diatomic molecule assuming a single covalent bond between two identical atoms

Question 17

Electronegativity

Answer 17

Strength which atoms of an element attract electrons when they are chemically combined with another element

Measured on the Pauling scale

Question 18

Electron Shielding

Answer 18

The repulsive force exerted by inner shell electrons on outer shell electrons, pushing them away from the nucleus

Question 19

First Ionisation Energy

Answer 19

The amount of energy required to remove an electron from each of a mole of gaseous atoms of that element

Question 20

Relative Isotopic Mass

Answer 20

The mass of an isotope relative to 1/12 of the mass of an atom of carbon‐12

Question 21

Relative Atomic Mass

Answer 21

The average mass of isotopes of that element, weighted for their abundance, relative to 1/12 of the mass of an atom of carbon‐12

Question 22

Mass Spectrometry

Answer 22

An analytical technique that can be used to measure the accurate mass of the isotopes of an element and the relative abundance of those isotopes

Question 23

ground state

Answer 23

all electrons are in the lowest possible sub-shell ( with respect to energy level)

Question 24

exited state

Answer 24

temporarily has 1 or more electrons in a higher energy sub shell than the lowest possible

Question 25

when atoms lose electrons which electron would be lost and why?

Answer 25

ouetermost electrons are lost becasue they have the highest energy ( eg. Li: 2,1 becomes Li+: [2]+)

Question 26

Trends in Atomic Radius

Answer 26

Atomic radius is influenced by two factors: 1) Number of occupied energy levels (shells) 2) Core charge

Question 27

As you move down a group the atomic radius increases

Answer 27

* the number of occupied energy levels increases | * core charge remains constant

Question 28

As you move across a period the atomic radius decreases.

Answer 28

* The number of occupied energy levels remains constant | * Core charge increases resulting in the valence electrons being more strongly attracted to the nucleus.

Question 29

Electronegativity will be higher when:

Answer 29

• The atomic radius is low – ie the number of occupied electron shells is low and there is room in the valence shell for a shared electron • The core charge on the atom is high – for the purposes of electronegativity this should be split into the two components, nuclear charge and electron shielding.

Question 30

As you move down a group the electronegativity decreases

Answer 30

• Number of occupied energy levels increases, therefore the atomic radius increases • Nuclear charge increases, however electron shielding (number of inner shell electrons) also increases so the core charge remains the same overall Therefore, the further down a group, the farther the outermost electron is from the nucleus and the more electrons an atom has between the outermost electron and the nucleus. All of this results in the outermost electrons (and any electrons participating in bonding) being attracted less towards the nucleus.

Question 31

As you move across a period the electronegativity increases

Answer 31

* Number of occupied energy levels stays constant, and the atomic radius decreases (due to increasing core charge) * Nuclear charge increases but number of inner shell electrons stays the same (shielding remains constant) so the core charge increases * Therefore, as we move across a period from metals to nonmetals, the valence electrons become more strongly attracted to the nucleus, increasing electronegativity.

Question 32

As you move down a group the first ionisation energy decreases

Answer 32

``` • the number of occupied energy levels increases so the atomic radius increases (and therefore nuclear attraction decreases) • Despite the nuclear charge increasing, electron shielding also increases so core charge remains constant • Therefore less energy is required to remove an electron. ```

Question 33

As you move across a period the first ionisation energy increases.

Answer 33

``` • The number of occupied energy levels remains constant, and the atomic radius decreases so the outermost electrons are closer to the nucleus. • Core charge increases resulting in the outermost electrons being more strongly attracted to the nucleus. • Therefore more energy is required to remove an electron. ```

Question 34

Trend across a period for Reactivity of Metals

Answer 34

When metals react they lose electrons (form positive ions). As we move across a period (LR): Core charge increases and electron shielding remains constant This results in a general increase in the energy required to remove an electron (increase in first ionisation energy). Therefore, the reactivity of the metals decreases across a period.

Question 35

Trend down a group for Reactivity of Metals

Answer 35

When metals react they lose electrons (form positive ions). As move down a group: Core charge stays the same Number of energy levels and electron shielding increases This results in a general decrease in the energy required to remove an electron. Therefore, the reactivity of the metals increase down a group.

Question 36

Isotopes

Answer 36

Atoms of the same element can have different numbers of neutrons (and therefore different mass numbers) Two atoms with the same atomic number, but different mass number are called isotopes.

Question 37

Nuclide Symbols

Answer 37

The nuclide symbol for an atom shows the atomic symbol (eg He), the atomic number and the mass number