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Atomic structure

Janine Bailey

Created on October 13, 2020

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Transcript

Presentation

ATOMIC STRUCTURE

Form 4 Chemistry

The basic building block of matter

ATOMS

VIDEO

A brief history on the development of the atom and all its particles

Sub Atomic Particles

Protons

Neutrons

Electrons

Found outside the nucleus orbiting the nucleus in shells. Have a relative charge of -1 Have a relative mass of 1/1836 or 1/1840 or sometimes it is written as 0

Found inside the nucleus Have a relative charge of +1 Have a relative mass of 1.

Found inside the nucleus Have a relative charge of 0 Have a relative mass of 1

1. Summary

Sub atomic particles

Atomic number is the number of protons in the nucleus of one atom of an element.

Nuclear notation is a way of showing both the mass number and atomic number of an atom of an element.

Mass number is the total number of protons and neutrons in the nucleus of one atom of an element.

CSEC Chemistsry by Anne Tindale page 18

VIDEO

Quick quiz

1. What element does the symbol represent?2. How many protons are found in one atom of this element? 3. How many electrons are found in one atom of this element? 4. How many neutrons are found in one atom of this element?

Electronic Structure/Electronic Configuration

The arrangement of electrons in energy levels or shells around the nucleus

Key points in drawing electronic configurations

When drawing electronic configurations1. Draw in your nucleus separately from your energy shells. Put the atom's symbol in the nucleus and write in the no of protons and neutrons as p=.. and n=.. 2. Start putting electrons in the lowest energy level first. 3. Add your electrons singly at first before you pair them up. Place them at the four cardinal points when drawing them singly 4. The maximum on the 1st shell is 2 and the other shells is 8 5. When WRITING electronic configurations, the order of filling shells is the same as when drawing and commas are placed between the numbers.

VIDEO

How to draw and write electron structure/configurations

So what exactly are ions?

Once the number of protons and electrons are NO LONGER EQUAL in at atom, the species is now called an ION. Ions are formed when atoms lose or gain valence electrons. Electrons are lost or gained when atoms bond with each other to get a full shell to become stable. In Chemistry, all things tend towards stability. (Valence electrons=electrons in the outer shell of the atom)

VIDEO

Let's practise.

Now that we understand how ions are formed, let's practise with an example.1. The atomic number of Na=11. What does that mean? Write down the electronic configuration of the Na atom 2. When sodium reacts, it forms a positive ion. What does that mean, does it lose or gain electrons? 3. How many electron(s) does sodium lose? Why does it lose only this amount? After it forms an ion, write down the number of protons and electrons in the sodium ion. Compare this with the sodium atom in question 1 above. Write or draw the electronic configuration of the sodium ion.

Practice time: Attempt the following questions below

Click here to see the answers

Let's talk isotopes

These are atoms of the SAME ELEMENT with the same number of protons but a different number of neutrons so the mass number is different.

Isotopes

So if an element contains many atoms and some of these atoms may have different mass numbers from each other, can we work out an average mass number for each element?

Question time

Calculating average mass numbers/relative atomic masses

1. Carbon has 3 naturally occuring isotopes with the following relative abundances 98.89% carbon-12, 1.10% carbon-13 and 0.01% carbon-14. Calculate its relative atomic mass (average mass number) to 3 d.p.2. Neon also has 3 isotopes of the following composition 90.48% neon-20, 0.27% neon-21 and 9.25% neon-22. Calculate its average mass to 3dp. Once you have attempted both questions click to see the correct answer

VIDEO 1

What's so special about isotopes anyway?Click here to see more. Refer to page 45-47 of CSEC Chemistry by Naresh Birju or page 21 of the Concise Chemistry by Anne Tindale

VIDEO

This video focuses on the disaster that happened at a nuclear power plant involving of a particular radioactive isotope Uranium 235

Thanks for viewing

Remember that an ion has a different number of electrons from the protons because the electrons AND ONLY THE ELECTRONS are lost or gained during chemical bonding A positively charged ion or cation will have less electrons than protons. So for Mg2+ the atomic number =12 It has 12 protons, but with a charge on the ion of 2+ , it means that we have 2 MORE PROTONS THAN ELECTRONS [or 2 less electrons than protons as 2 electrons were lost]. The number of electrons=10 A negatively charged ion or anion will have more electrons than protons. So for Cl- with a charge on the ion of 1-, it means that we have ONE MORE ELECTRON THAN PROTONS. The atomic number will first be found by subtracting the mass number 35 and the number of neutrons 18, 35-18=17. There are 17 protons but because it is Cl- as explained above, we will have 18 electrons.