The Atom & Bohr Model

The Atom

• Matter is anything that takes up space and has mass.

• We are carbon based lifeforms!

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Atoms are known as the building blocks of all matter

Subatomic Particles

Subatomic particles are what makes an atom up.

The atom consists of three main parts;
- Neutrons
- Protons
- Electrons

Electrons are negatively charged subatomic particles which orbit the nucleus.

Imagine the earth orbiting the sun for instance!

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Electrons

• Protons and Neutrons are both found in the nucleus (the centre of the atom).

• Protons are positively charged (+1) and Neutrons are Neutral (0)

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​Protons & Neutrons

• Located in Nucleus

• Positively charged (+)

​Protons

• Surrounding the nucleus, travelling in fixed pathways called orbits

• Negatively charged (-)

Electrons

• Located in nucleus

• Neutral charge (0)

​​Neutrons

Poll

How many atoms do you think make up one grain of sand?

• 999,999

• 47372829292827273

• 100,000,000,000,000,000,000 (10²⁰)

• 105

Match

Match up the following parts of the atom

• Negatively charged subatomic particle

• Positively charged subatomic particle

• Neutral charged subatomic particle

• Fixed pathways which electrons travel

• The centre of the atom , composed of protons and neutrons

Electron

Proton

Neutron

Orbits

Nucleus

• Electron

• Proton

• Neutron

• Orbits

• Nucleus

Elements are substances made up of only one atom, like Gold (Au) or Lead (Pb).

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Identifying Elements

• The smaller number always represents the atomic number.

• This number shows the number of protons in that element.

• In this case, the atomic number of sodium is 11.

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Atomic Number

• The larger number always represents the mass number.

• This number represents the amount of protons and neutrons in an element.

• In this case, the mass number of carbon is 12. (12.011)

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Mass Number

Multiple Choice

What is the ATOMIC NUMBER of this element?

• 40

• 55

• 20

• 10

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Multiple Choice

What is the MASS NUMBER of this element?

• 4

• 5

• 2

• 1

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Multiple Choice

What is the ATOMIC NUMBER of this element?

• 10.5

• 10

• 5

• 10.81

When referring to elements, we usually use their atomic numbers as a reference.

For example, Carbon has an atomic number of 6, therefore we'd say it is the '6th element'.

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​Using the Periodic Table

Draw

Using the periodic table in your journals, find the element potassium (symbol K) and draw the element box for potassium. Include the atomic number and the mass number.

Multiple Choice

Which element has an atomic number of 7?

• Oxygen

• Helium

• Argon

• Nitrogen

Multiple Choice

Which element has an atomic number of 19?

• Potassium

• Helium

• Argon

• Flourine

Multiple Choice

Which element has the symbol 'Cl' ?

• Carbon

• Chlorine

• Chromium

• Flourine

Multiple Choice

Which element has the symbol 'Ca' ?

• Carbon

• Chlorine

• Cobalt

• Calcium

Multiple Choice

Which element has an atomic number of 13?

• Silicon

• Neon

• Aluminium

• Carbon

Match

Match the following elements to their symbols

• Argon

• Chlorine

• Carbon

• Silicon

• Sodium

Ar

Cl

C

Si

Na

• Ar

• Cl

• C

• Si

• Na

• A famous Danish scientist named Niels Bohr investigated the arrangement of electrons in an atom.

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Bohr Model & Atomic Structure

• The first shell (or orbit) can hold two electrons.

• The second shell (or orbit) can hold eight electrons.

• The third shell (or orbit) can hold eight electrons.

• The fourth shell (or orbit) can hold 18 electrons.

Bohr Model

• Helium has 2 electrons (atomic number of 2).

• We place these 2 electrons in the first orbit.

• We say the electron arrangement is {2}

Bohr Model

• Carbon has 6 electrons. Atomic number is 6.

• We place 2 electrons in the first orbit. We place the remaining 4 electrons in the second orbit.

• We say the electron arrangement is {2,4}

Bohr Model

• Sodium has 11 electrons. Atomic number is 11.

• We place 2 electrons in the first orbit. We place the next 8 electrons in the second orbit. There is still one electron left over, we place this in the third orbit.

• We say the electron arrangement is {2,8,1}

Bohr Model

Draw

Draw the Bohr model for Nitrogen.

Draw

Draw the Bohr model for Neon (Ne).

Draw

Draw the Bohr model for Calcium (Ca).