chemistry (14 - 16) the atom (basic structure - 2) © sser ltd

Chemistry(14 - 16)

Chemistry(14 - 16)

The Atom(Basic Structure - 2)The Atom

(Basic Structure - 2)© SSER Ltd.

The electron levels fill as we move across and down the Periodic Table.

Electronic StructureElectronic Structure

In Group 1 of the Periodic Table, all of the elements have one electron in their outer shell.

This similarity in electron structure explains the fact that the elements in Group 1 have similar chemical properties.

Group 1 - Electronic StructureGroup 1 - Electronic Structure

Li3

2,1

Na11

2,8,1

K19

2,8,8,1

Rb37

2,8,18,8,1

Cs55

2,8,18,18,8,1


Group 1 elements all have similar chemical properties, but the presence of an increasing number of complete electron shells inside the outer level does affect the properties.

Li3

2,1

Na11

2,8,1

K19

2,8,8,1

Rb37

2,8,18,8,1

Cs55

2,8,18,18,8,1

In most of their chemical reactions, the atoms release this electron and become positively charged ions.


Lithium reacts with cold water on contact and slowly dissolves to form a solution of lithium hydroxide.

Caesium reacts explosively on contact with cold water to form a solution of caesium hydroxide.

As we descend the group, the metals become more reactive.

Li3

2,1

Na11

2,8,1

K19

2,8,8,1

Rb37

2,8,18,8,1

Cs55

2,8,18,18,8,1

In Group 7 of the Periodic Table (Halogens) all of the elements have an incomplete outer shell - one electron is needed to complete it.This similarity in electron structure gives the elements in Group 7 similar chemical properties.


F9

Cl17

Br35

I53

2,7

2,8,7

2,8,18,7

2,8,18,18,7

Group 7 elements all form diatomic molecules, e.g. F2, Cl2.


F9

Cl17

Br35

I53

2,7

2,8,7

2,8,18,7

2,8,18,18,7

As the group is descended, the elements become less reactive.

The elements in Group 7 all form diatomic molecules, e.g. F2, Cl2.

They are all colourful non-metals.

In Group 0 of the Periodic Table, all of the elements have full outer shells of electrons.

This similarity in electron structure explains gives the elements in Group 0 similar chemical properties.

The elements are unreactive and monatomic (single atoms).


He2

Ne10

Ar18

Kr36

Xe54

2

2,8

2,8,8

2,8,18,8

2,8,18,18,8

In Group 0 the elements all have similar chemical properties, but the presence of an increasing number of complete electron shells does affect their properties.

As the group is descended, the gases become heavier and ‘more’ reactive.

Helium and Xenon have no known natural compounds.


He2

Ne10

Ar18

Kr36

Xe54

2

2,8

2,8,8

2,8,18,8

2,8,18,18,8

A Space Filling Model ofXenon Tetrafluoride

A Space Filling Model ofXenon Tetrafluoride

Although Xenon has no known natural compounds, it can beinduced to react with Fluorine under extreme conditions.

Electron Levels (Shells)Electron Levels (Shells)

Drag the electronic configurations and names into the correct places for the elements below…

Electron Levels (Shells)Electron Levels (Shells)Drag the electronic configurations and names into the correct places for the elements below…

Li3

B5

N7

C6

O8

F9

Ne10

Be4

If we examine the elements in the first short period of the Periodic Table we can see a pattern in their atomic number...

1st Short Period - Electronic Structure1st Short Period - Electronic Structure

Across the Periodic Table (left to right), the atomic number increases by one each time.

As the atomic number is also the same as the number of electrons in an atom – then the number of electrons also increases with the increase in atomic number.

The numbers below each atom are the electron configurations of the atoms, e.g. the electron configuration of a carbon atom is 2,4.

This means that a carbon atom has two electrons in the first level and four electrons in the second level.

1st Short Period - Electronic Structure1st Short Period - Electronic Structure

The electron configuration of a sulfur atom is 2,8,6.

This means that a sulfur atom has:...two electrons in the first level......eight electrons in the second level......six electrons in the third level.

2nd Short Period - Electronic Structure2nd Short Period - Electronic Structure

Electronic Structure - PropertiesElectronic Structure - Properties

The elements change gradually in both physical and chemical properties across the period from left to right.

The elements on the left are metallic elements, and the elements to the right are non-metallic.

Electronic Structure - PropertiesElectronic Structure - Properties

Sodium is areactive metal

Chlorine is areactive gas

Argon is anunreactive gas

Electronic Structure and Chemical PropertiesElectronic Structure and Chemical Properties

The electronic structures dictate that

elements with only a few electrons in their outer levels (e.g. Na, Mg, Al) can most easily lose electrons, gaining an inert gas configuration and thus form positive ions.

Electronic Structure and Chemical PropertiesElectronic Structure and Chemical Properties

Elements with nearly complete outer shells (e.g. Cl) can most easily gain electrons, gaining an inert gas configuration and thus form negative ions.The inert gases (e.g. Ar) have a complete outer electron shell and so are unreactive.

Elements differ from one another in that their atoms contain different numbers of the sub-atomic particles. The number of protons (or the atomic number) of an atom, is the factor which decides the identity (element) of an atom.

All Lithium atoms have 3 protons.All Carbon atoms have 6 protons.All Uranium atoms have 92 protons.

What Determines The Element?What Determines The Element?

For each element in turn, calculate the missing entries...

Atom Symbol Atomic No. Mass No. Protons Neutrons Electrons

Hydrogen H 1 1

Helium 2 4

Carbon 6 12

Chlorine 17 37

Calcium 20

Copper 64 29

Zinc 30 65

Tin 50

Tungsten 74 184

Radon 86 136

1 0 1

He 2 2 2

C 6 6 6

Cl 17 20 17

Ca 40 20 20 20

Cu 29 35 29

Zn 30 35 30

Sn 119 50 69 50

W 74 110 74

Rn 222 86 86

Calculate the Particles in an Atom

Atomic Structure and the Periodic TableAtomic Structure and the Periodic Table

Li3

B5

N7

C6

O8

F9

Ne10

Be4

Cl17

If we examine the elements in the two short periods of the periodic table we can see a pattern in their atomic number...

11Na

12Mg

14Si

13Al

16S

15P

18Ar

Elements are arranged in the Periodic Table in order of the number of protons present in the nucleus (atomic number).Across the periodic table (left to right) the atomic number increases by one each time. The number of electrons is the same as the atomic number.

The mass of an atom is mainly in the nucleus. Protons and neutrons have an equal mass of one atomic mass unit. Electrons have negligible mass. Therefore, the mass of an atom is equal to the sum of the number of protons and neutrons. This number is called the mass number of the atom.

However, some atoms of carbon have different numbers of neutrons. Atoms of the same element with different numbers of neutrons are called isotopes of that element.

IsotopesIsotopes

For example, carbon atoms each have six protons and six neutrons, and therefore the atomic mass is twelve atomic mass units. The mass number of the most common carbon atom is 12.

Therefore, isotopes of the same element have their own mass number.

12

6C

Mass Number

Atomic Number

The Carbon IsotopesThe Carbon Isotopes

14

6C

The carbon 12 isotope has 6 protons, 6 neutrons and 6 electrons

The carbon 14 isotope has 6 protons, 8 neutrons and 6 electrons

= Neutron = Proton = Electron

For each isotope, calculate the missing entries...

Isotope Symbol Atomic No. Mass No. Protons Neutrons Electrons

Hydrogen H 1 1

Hydrogen(Deuterium)

H 1 1 1

Hydrogen(Tritium)

H 1 3

Carbon 12 6 12

Carbon 14 C 6 14

1 0 1

C

6 8 6

Calculating the Atomic Particles in IsotopesCalculating the Atomic Particles in Isotopes

6 6 6

1 2 1

12

SummarySummary1. Atoms are tiny and in constant motion.

2. Atoms are composed of a nucleus (contains protons, neutrons) and orbiting electrons.

3. The nucleus contains most of the mass of the atom.

4. The number of particles an atom contains determines the identity of the atom.

5. The atomic number of an atom is equal to the number of protons in its nucleus.

6. The mass number of an atom is equal to the number of protons plus neutrons in its nucleus.

7. Atoms have the same number of protons as electrons, so their overall charge is neutral.

chemistry (14 - 16) the atom (basic structure - 2) © sser ltd

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