Atomic Strc

Learning Outcomes of the lesson:

• define isotopes• state the two types of isotopes as being radioactive and non-

radioactive• state one medical and one industrial use of radioactive isotopes• describe the build-up of electrons in ‘shells’ • understand the significance of the noble gas electronic

structures and of valency electrons• understand the relation between the Periodic Table and the

electronic configuration

• Hydrogen - Different atoms of the same element???

• ISOTOPES!!!!!

Protium

So… How can we define an isotope?

• Isotopes – atoms of the same element, with different numbers of neutrons.

• Most elements has isotopes.

• Carbon-12: 6 protons, 6 electrons, 6 neutrons• Carbon-13: 6 protons, 6 electrons, 7 neutrons • Carbon-14: 6 protons, 6 electrons, 8 neutrons

• Carbon-14 is radioactive – its nucleus is unstable; is breaks down or decays, giving out radiation and energy.

• It is a radioisotope.• The C-12 and C-13

are non-radioactive isotopes.

Are radioisotopes useful or harmful?

• Scientists now how long it takes for half the radioisotopes in a sample to decay. This is called the half-life.

• Half life of…– C-14 is 5730 years– Radon-220 is 55.5 seconds– Potassium-40 is 1300 million years

– The radiation they release is able to kill body cells, but if used with extreme safety, radioisotopes can be useful!

Making use of radioisotopes

• To check for leaks in oil and gas pipes (for example);

• In cancer treatment;• To find the age of old remains (the process is

called carbon dating)

Questions –

page 31

• An electron shell may be crudely thought of as an orbit followed by electrons around an atom nucleus.

• Each shell is associated with a particular range of electron energy, and thus each shell must fill completely before electrons can be added to an outer shell.

• The electrons in the outermost shell (valency electrons) determine the chemical properties of the atom

• 1st shell: 2 electrons• 2nd shell:8 electrons• 3rd shell: 8 electrons

And what about the Periodic Table?• The Periodic Table arranges the elements in order of atomic number.

• Elements with similar properties line up in vertical columns. These columns are known as groups. There are 8 groups in the Periodic Table.

• A row across the Periodic Table is known as a Period.• The group number show how many valency electrons exist

(exception, Group 0).

• The period number shows how many shells there are.

Questions – Page 37

Learning Outcomes of the lesson:

review the differences between elements, mixtures and compounds, and between metals and non-metals

describe an alloy, such as brass, as a mixture of a metal with other elements describe the formation of ions by electron loss or gain describe the formation of ionic bonds between elements from Groups I and

VII understand how a formulae of an ionic compound is make understand that some transition metals can form more that one type of atom understand what is a compound ion understand the properties of the ionic compounds

Compound

Element

Mixture

Most of the elements form compounds…

What it is an alloy?

• An alloy, such as brass, is a mixture of a metal with other elements.

Some alloys are made by melting and mixing two or more metals.

Brass is an alloy made from copper and zinc. Bronze, used for statues, ornaments and church bells, is an

alloy of tin and copper.Steel is a metal alloy whose major

component is iron, with carbon

sodium + chlorine sodium chloride

+ means reacts with means to form

Now, use circles to show the electronic shells of sodium and chlorine.

Then do the same thing for chloride ion and for sodium ion.

Ionic Bond• When two ions have opposite charges, they attract to each other. The force of attraction

between them is strong.

• It is called an ionic bond.

What is the overall charge of NaCl compound?

• What about:

Magnesium + Oxygen Magnesium Oxide ???

Draw the electronic shells!!!

• What about:

Magnesium + Chlorine Magnesium Chloride ??

Draw the electronic shells!!!

Open your textbook and fill in the spaces:

• Hydrogen and the metals form ______ ions; these have the same names as the _____.

• The non-metals form _____ ions, and their names end in ______.

• The elements in Groups 4 or 5 do not usually form ions, because _____________________________________.

• Group 0 elements do not form ______.

Give them names…

• K+ and F-

• Mg2+ and S2-

• What about transition metals? Do they form ions?

Compound Ions• Compound ions – ions that are formed from groups

of joined atoms.

Examples:

• NH4+ ammonium ion

• OH- hydroxide ion

• NO3- nitrate ion

• SO42- sulphate ion

• CO32- carbonate ion

• HCO3- hydrogencarbonate ion

Properties of Ionic Compounds

• Ionic compounds have high melting and boiling points;

• Ionic compounds are usually soluble in water;

• Ionic compounds can conduct electricity, only when they are melted or dissolved.