4. The Periodic Table

Question 1

What did the Greeks believe about elements?

Answer 1

4 elements: earth, fire, air , water

EFAW

Question 2

What scientist in 1661 gave a simple definition of an element?

Answer 2

Robert Boyle, from Waterford

Question 3

Element

Answer 3

An element is a substance that cannot be split into simpler substances by chemical means

Question 4

Which scientist in 1829 put elements with similar properties in triads?

Answer 4

Dobereiner

Question 5

Triad and the problem with this theory

Answer 5

A triad is a group of three elements with similar chemical properties in which the atomic weight (relative atomic mass) of the middle element is approximately equal to the average of the other two.
Eg Lithium Sodium Potassium (group1)
Prob: few other triads found

Question 6

Who was the first scientist to arrange elements in order of increasing atomic weight in 1864?

Answer 6

Newlands

Question 7

Newland’s octaves

Answer 7

Newland’s octaves are arrangements of elements in which the first and the eighth element, counting from a particular element, have similar properties.

Question 8

Mendeleev’s Periodic Law

Answer 8

When elements are arranged in order of increasing atomic weight, the properties of elements recur periodically
I.e the properties displayed by an element are repeated at regular intervals by other elements

Question 9

What 3 things did Mendeleev do?

Answer 9

1. He left gaps for undiscovered elements and correctly predicted their properties
2. He switched some pairs of elements around to make sure they would fit in with the properties expected of that group
3. Transition metals did not have a separate block

Question 10

Which scientist arranged elements in order of increasing atomic number in 1913?

Answer 10

Moseley

Question 11

Atomic number

Answer 11

Atomic number of an atom is the number of protons in the nucleus of the atom

Question 12

Modern Periodic Law

Answer 12

When elements are arranged in order of increasing atomic number, the properties of elements recur periodically
I.e the properties displayed by an element are repeated at regular intervals by other elements

Question 13

What are 2 features singular to Moseley’s periodic table?

Answer 13

• No gaps

- Transition metals have a separate block

Question 14

Mass number

Answer 14

The mass number of an element is the sum of the number of protons and neutrons in an atom of that element.

Question 15

How to calculate no. of neutrons

Answer 15

Neutrons : Mass no. - Atomic no.

Question 16

What is the chemical symbol for mass no.?

Answer 16

A

Question 17

What is the chemical symbol for atomic no.?

Answer 17

Z

Question 18

Isotopes

Answer 18

Isotopes are atoms of the same element (they have the same atomic no.) which have different mass no. due to the different no. of neutrons in the nucleus

Question 19

Relative atomic mass

Answer 19

• the average of the mass no’s of the isotopes of an element,
• as they occur naturally,
• taking their abundances into account
• and expressed on a scale relative to 1/12th the mass of 12C.

Question 20

Principle of mass spectrometry

Answer 20

The principle of mass spectrometry is that charged particles moving in a magnetic field are deflected to different extents according to their masses and are thus separated according to these masses.

Question 21

What are the 5 stages of mass spectrometry?

Answer 21

1. Vaporisation
2. Ionization
3. Acceleration
4. Separation in the magnetic field (analyser)
5. Detection

Question 22

Vaporisation

Answer 22

Liquid sample is turned to gas in the vacuum

Question 23

Ionization

Answer 23

High energy electrons are fired from an electron gun to knock out electrons from atoms of the sample, leaving cations in their place

Question 24

Acceleration

Answer 24

Cations pass through a series of negatively charged plates. These plates attract the pos.ions, thus accelerating them into the analyser unit as a fine beam.

Question 25

Separation in the magnetic field

Answer 25

an electromagnet is used to deflect ions. Lighter ions are easier to deflect, heavier ions harder. Thus ions are separated into separate beams according to their masses.

Question 26

Detection

Answer 26

Ions fall on detector. Detector amplifies signal into sizeable electric current which can be viewed on a computer screen. By changing strength of magnetic field, ions of different masses fall on detector, producing a mass spectrum.

Question 27

Uses of mass spectrometer , social use

Answer 27

-identify presence of isotopes -identify unknown compounds -measure relative abundance of isotopes + relative atomic mass ——— test for drugs , athletes, Garda

Question 28

Electron configuration

Answer 28

The electron configuration shows the arrangement of electrons in an atom of an element .

Question 29

Aufbau principle

Answer 29

When building up the electron configuration of an atom in its ground state, the electrons occupy the lowest available energy levels.

Question 30

Which two elements are special in their electronic configurations ? How? And why?

Answer 30

Copper (Cu): 4s1, 3d10 Chromium (Cr): 4s1, 3d5 Sub levels that are half filled or completely filled have extra stability, so an electron from the 4s “flips” over

Question 31

Hund’ s rule of Maximum Multiplicity

Answer 31

When two or more orbitals of equal energy are available, the electrons occupy them singly before filling them in pairs.

Question 32

Pauli Exclusion Principle

Answer 32

states that .. no more than two electrons can occupy an orbital and they must have opposite spin.

Question 33

What are the names of the orbitals in the p sublevel?

Answer 33

Px, py, pz