Atomic structure and properties

Question 1

Who was James Dalton?

Answer 1

Father of the atom

• Revisited the theory of the atom in 1808 and created his own
• He stated that they were hard, solid, impenetrable, moveable particles

Question 2

Who was Joseph Thomson?

Answer 2

Discovered negatively charged electrons through cathode ray experiment
-created the plum pudding model to explain his findings

Question 3

Who is Rutherford?

Answer 3

Discovered nuclei in atoms

• fired positively charge alpha particles at gold foil
• concluded that nuclei were small and dense when some bounced back

Discovered the proton

Question 4

Who was James Chadwick?

Answer 4

Discovered the neutron

-through bombardment of beryllium with alpha particles

Question 5

Who was Neils Bohr?

Answer 5

Proposed a new electron configuration (Bohr model)

• electron revolve around the nucleus at fixed distances
• orbit corresponds to specific energy level
• electron cannot exist between levels
• furthest orbit is highest energy level

Question 6

What is RAM?

Answer 6

Relative atomic mass

Question 7

What is an isotope?

Answer 7

Two or more forms of an element that contain the same number of protons but different neutrons.

• identical chemical properties
• different mass number

Question 8

How do stable isotopes occur?

Answer 8

-balance between attractive and repulsive forces in the nucleus

Question 9

How do isotopes become unstable?

Answer 9

When the forces in the nucleus are unbalanced

Question 10

Define isotopic composition

Answer 10

Shows isotopes which are present in a sample to what %/

e.g.( mass(%) + mass(%) )/100

Question 11

What is mass spectrometry?

Answer 11

Used to qualitatively and quantitively identify elements present in a compound or mixture

Question 12

What is the process of mass spectrometry?

Answer 12

Vaporising-separation of substance to gas state
Ionising-gas phase atoms then ionised (now have a charge)
Accelerating-pass through electric field to accelerate
Deflecting-charge deflected in magnetic field (more mass=less deflection)
Detecting-ions are analysed after being collected and abundance is measured

Question 13

How is an atom held together?

Answer 13

Electrostatic attraction between the opposing protons and electrons

Question 14

How is the nucleus held together?

Answer 14

Strong nuclear forces that occur regardless of change as well as electrostatic repulsion

Question 15

What is atomic number?

Answer 15

Number of protons in the nucleus

Question 16

What is mass number?

Answer 16

Number of protons and neutrons in the nucleus

Question 17

What is an ion?

Answer 17

A positively/negatively charged atom or group of atoms

Question 18

What is electrostatic attraction? and it’s periodic table trend?

Answer 18

Attraction between positive and negative charges in the atom that form chemical bonds

• increase charge difference=higher attraction
• inversely proportional to the distance between charges
• proportional to charge magnitude

Question 19

What is core charge? and it’s trend

Answer 19

Effective nuclear charge felt by an outer electron and proton in the nucleus

• equal to nuclear charge - total number of electrons in inner shell
• remains constant down a group
• increase across a period

Question 20

Explain the core charge trend

Answer 20

Increase across period:

• shielding stays same
• protons and electrons increase
• attraction increases

Same down group:

• ratio of electrons and protons being increased is proportional
• so no increase in attraction

Question 21

What is atomic radius? and it’s trend?

Answer 21

Measured as the distance from nucleus to the outer shell

• decrease across period
• increase down a group

Question 22

Explain the atomic radius trends

Answer 22

Decrease across a period:

• protons and electrons increase
• attraction therefore increases to the electrons
• shielding stays the same
• radius will decrease

Increase down a group:

• shell number increases
• decrease in attraction to valence electrons

Question 23

What is first ionisation energy? trend?

Answer 23

The energy required to remove the first valence electron from an atom of an element in it’s “gaseous state”

• increase across a period
• decrease down a group

Question 24

Explain the ionisation energy trend

Answer 24

Increase across a period:

• core charge increases (due to number of p and e increasing while shielding is same)
• electrons becomes harder to remove

Decrease down a group:

• atomic radius increases
• weaker attraction between nucleus and electrons
• electrons easier to lose

Question 25

What is successive ionisation energy?

Answer 25

Energy required to remove remaining electrons after the first valence electron is removed from an element in it’s gaseous state
decrease in atomic radius=increase energy required to ionise valence electrons

Question 26

What is shielding?

Answer 26

The decrease in attraction between an electron and the nucleus in any atom with more than one electron shell
-decreases electrostatic attraction

Question 27

What is electronegativity?

Answer 27

The ability of an atom to attract a pair of electrons in a covalent bond

Question 28

Explain electronegativity trends

Answer 28

Increases across a period:

• core charge increases
• radius decreases
• shielding stays the same while protons increase
• attraction therefore increases between valence electrons and the nucleus

Question 29

What is metallic character?

Answer 29

Describes how closely an element exhibits properties associated with metals
-readily loses an electron to form a cation
-bottom left of the periodic table
small ionisation energy=greater metallic character