C3 Atomic Structure & the Periodic table

Get your periodic tables out!Elements song!

http://www.privatehand.com/flash/elements.html

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The Periodic TableThe Periodic Table

The Periodic Table

Groups & periods (rows)

If a substance is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron

These atoms are ALL iron – there’s

nothing else in here

C3/3.3 Learning Objectives

• Describe the structure of an atom in terms of electrons and a nucleus containing protons & neutrons.

• State the relative charges & approximate relative masses of protons, neutrons and electrons.

• Define proton number & nucleon number.• Use proton number and the structure of an atom to

explain the basis of the periodic table with reference to first 20 elements

• Define Isotopes.

Learning Objectives

• Describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of valency electrons.

1) Atoms!

People thought that atoms were the smallest particles and could not be broken into anything smaller.

proton neutron electron

What can you say about the size of the electron compared to the neutron & proton

Atoms are the basic building blocks of matter that make up everyday objects.

What do you know…• Form a giant atom.• Atoms consist of protons, neutrons &

electrons-form a giant atom as a class or as groups

What is the structure of an atom?Protons, neutrons and electrons are not evenly distributed in an atom.

The electrons are spread out around the edge of the atom. They orbit the nucleus in layers called shells.

The protons and neutrons exist in a dense core at the centre of the atom. This is called the nucleus.

Pea in a football pitch

Mass and electrical chargeThere are two properties of protons, neutrons and electrons that are especially important:

mass

electrical charge.

-1almost 0electron

01neutron

+11proton

ChargeMassParticle

Mass Number - The larger number.

Mass number= number of protons + number of neutrons

Atomic Number/ Proton Number-Number of protons equals number of electrons.

What is sodium’s atomic number?How many protons does it have?How many electrons does it have?What is its Mass Number?

How many neutrons does it have?number of neutrons = mass number - number of protons = mass number - atomic number

=23 – 11 =12 Neutrons

2) Atomic Number & Mass Number (Nucleon number)

Periodic table• Elements in the periodic table are

arranged in order of atomic number!

Mini-WhiteboardsHydrogen

1 proton

0 neutrons

1 electron

Fluorine9 Protons

9 Electrons

10 Neutrons

Magnesium12 Protons

12 Neutrons

12 Electrons

Carbon6 Protons

6 Neutrons

6 Electrons

Oxygen

8 Protons

8 Neutrons

8 Electrons

Iron

26 Protons

30 Neutrons

26 Electrons

Tin

50 Protons

69 Neutrons

50 Protons

Equal numbers of protons and electronsAtoms of elements have no charge, they are neutral.

What is the charge on a fluorine atom?

1919

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How are the number of electrons and atomic number related in a neutral atom?

9 protons 9 electrons10 neutrons

charge = +9 charge = - 9 charge = 0

Total charge = 0

They are the same.

Isotopes• Different forms of the same atoms can exist.• These are called Isotopes

• Isotopes are different forms of the same element that have the same atomic number but different mass numbers.

IsotopesAn isotope is an atom with a different number of neutrons:

Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.

Notice that the mass number is different. How many neutrons does each isotope have?

Progress check1) Name the sub-atomic particles within an atom. (3)

2) Explain why atoms are overall neutral in charge. (2)

3) Complete the missing numbers (11)

Self assessed answers

1)Protons, neutrons & electrons.2)Atoms are neutral as protons (positive charge) are equal to the number of electrons (negative charges)3) Boron-5,11Potassium 19,20Chromium 24,52Mercury 80,80Argon 18,22,18

Question 4: Identifying Isotopes

4a) What is an isotope?

4b)Identify the isotopes from data about the number of electrons, protons and neutrons:

1) 1 proton, 1 electron, 2 neutrons2) 1 proton, 1 electron, 1 neutron3) 17 protons, 17 electrons, 19 neutrons4) 85 protons, 85 electrons, 126 neutrons

H31 H2

1 Cl3617 At211

85

3) Electrons

• The protons & Neutrons are found in the............

• Electrons have a special home of their own.

Electrons are found on ENERGY LEVELS also known as Shells!

These energy levels can only house a certain number of electrons.

Electron ShellsElectrons will fill the shells nearest the nucleus first.

1st shell holdsa maximum of2 electrons

2nd shell holdsa maximum of8 electrons

3rd shell holdsa maximum of8 electrons

This electron arrangement is written as 2,8,8.What if you have more than 18 electrons..where does the extra electron go?...

Tasks • Mats & Play Dough

• Take a tub between 3 and use this to represent your electrons.

• Complete the electron arrangement for the following:F, Mg, Si,

Extension: (Ar, Ca)

Electron arrangement• Electron configuration for first 20

elements. • Draw and write it down, eg, 2,8,1

Question Table 1 Table 2 Table 3 Table 4

1-2 Anika & Moushomi

Sayeeda &Shamina

Syeda H & Rahima

Adama &Shaheena

3-4 Leigh & Shahnaz

Samiha & Nadia

Sadia & Sima

Momtaz & Abisola

5-6 Fahmida &Cara

Ruma & Shema

Nasima Forida

Extension questions

Answers• Q1-All have 1 outer electron.• Q2-Both have 7 electrons in their outer shell• Q3-The group number tells us the number of outer electrons.• Q4-Group 8 Noble gases-unreactive• Q5-Iodine-7• Arsenic-5• Barium-2• Q6-First electron furthest away easiest to remove. Greater distance

between electrons and nucleus.• Next eight increasingly harder to remove.• Next 2 closest to shell-hardest-greater nucleus attraction-shorter distance

from nucleus to electrons.

Giant atom• Form a giant atom using what you

have learnt today.

Exam quest

Questions- linked to learning objectives

Learning objectives-linked to exam quest

• (D) Describe the structure of the atom in terms of protons, neutrons and electrons. Question 1

• (C) Identify symbols and atomic numbers using a Periodic Table. (C) State that elements are arranged in ascending atomic number. Question 2& 3

• (B) Identify the group of an element from its outer electrons and row from it shells. Question 4

• (B) Deduce the number of protons, neutrons and electrons in a particle and identify isotopes. Question 5

• (B) Deduce the electronic structure of the first 20 elements. Question 6

• (A) Explain why an atom has a neutral charge. Question 7 if you can answer WHY? To part 7bii-even better!

Giant atom• Form a giant atom using what you

have learnt today.

Extras

Building a nucleus

Summary: the atom so farThe nucleus is: Made up of protons and neutrons Positively charged because of the

protons Dense – it contains nearly all the

mass of the atom in a tiny space.

Electrons are: Very small and light, and negatively charged Able to be lost or gained in chemical reactions Found thinly spread around the outside of the nucleus,

orbiting in layers called shells.