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Flashcards in Periodicity and group 2 Deck (26)
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1
Q

What does the atomic number tell us about an element?

A

Number of protons in an atom

2
Q

How is mass number calculated?

A

Number of protons + number of neutrons

3
Q

Define relative atomic mass

A

Average mass of all isotopes of an element compared to 1/12 the mass of am atom of carbon12

4
Q

What is an isotope of an element?

A

Different forms of the same element, containing the same number of protons but different numbers of neutrons. They still have the same chemical properties.

5
Q

Name the number of orbitals

A

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

6
Q

Does 3D or 4s have a higher energy?

A

3D

7
Q

What is an orbital?

A

A region around the nucleus that can hold up to two electrons

8
Q

What would be the relationship between 2 electrons in the same orbital in terms of their spin?

A

Have opposite spin as repel each other as both negative

9
Q

Explain why chromium does not fit the trend for electronic configuration

A

It only has one electron in its 4s orbital before filling 3D

10
Q

Explain why cooper does not follow the trend for electronic configuration

A

It only has one electron in its 4s orbital before 3d

11
Q

What are the two types of ionisation for a mass spectrometer? How do they differ?

A

1) electron impact- electron gun knocks odd one electron from each particle to form each 1+ ion
2) electron spray- sample dissolved in volatile solvent and injected through a fine needle which is attached to a high voltage, it gains a proton producing XH+ ions

12
Q

When would you use the different types of ionisation in a mass spec?

A

Electron impact is used for substances with a low formula mass
Electron spray is used for substances with a high molecular mass

13
Q

Describe how a time of flight mass spec works

A

Acceleration- positive ions attracted towards a negatively charged plate
Ion drift- ions pass through hole in plate, form a beam with constant kinetic energy, travel along tube to detector. Time of flight is therefore directly proportional to the square root of mass
Detection- positive ions pick up electrons, current flows m/z value and time of flight recorded. Largest current from most abundant ions

14
Q

Define first Ionisation energy

A

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions

15
Q

Explain the graph of first ionisation energy of group 3

A

Increases across group 3 because of increase in nuclear charge, decreased atomic radius and same electron shielding means more energy is needed to remove first electron.
Dips at Al because outer electron is in a 3p orbital which has a higher energy than 3s
Dips at S because one 3p orbital contains two electrons and there is a repulsion between the paired electrons

16
Q

Describes ionisation energy down group 2

A

Decreases because number of filled electron shells increases down the group so increased shielding so increases atomic radius so weaker force between electrons and nucleus

17
Q

How does reactivity with water change as you go down group 2?

A

Mg least
Ba most
Because outer electrons are further away from nucleus and more electron shielding so electrons are lost more easily

18
Q

Write an equation for the reaction of Ba and water

A

Ba + 2H2O -> Ba(OH)2 + H2

19
Q

Equation between Mg and steam

A

Mg + H2O -> MgO + H2

20
Q

What is the trend in hydroxide solubility down group 2?

A

Increases down the group
Mg(OH)2 is almost insoluble
Ba(OH)2 creates a strong alkaline solution

21
Q

What is the trend in sulphate solubility down group 2?

A

Decreases down group
MgSO4 is soluble
BaSO4 is insoluble

22
Q

Trend in melting point down group 2

A

Decreases because sea of delocalised electrons is further away from nucleus so weaker metallic bonds

23
Q

What is the trend in atomic radius down group 2

A

Increases as there are more occupied shells

24
Q

What is Ca(OH)2 used for

A

Neutralise soil

25
Q

What is Mg(OH)2 used for

A

Antacid to treat indigestion

26
Q

What is a use of BaSO4

A

Barium meals to outline gut in X-rays