Atoms Elements and Compounds Chapter 22

An Element An Element is a substance that cannot be broken down into simpler substances by chemical means. If we examine all the materials in the world around us we would find that there are about 100 elements from which everything is made. All of the elements known at the present time are listed in a table called the Periodic Table of Elements

The Periodic Table of Elements

Atoms All substances are made up of tiny particles called Atoms An Atom is the smallest part of an element that still has the properties of that element.

Elements

Some common Elements and their uses

Compounds What is a Compound? A Compound is formed when two or more elements combine together chemically. Although there are only a little over 100 elements there are millions of compounds.

Examples of Compounds

A Molecule A molecule is the smallest part of an element or compound that can exist on its own. Examples of Molecules of Elements:

Molecules of Compounds A molecule of water is made up of two atoms of Hydrogen and an atom of Oxygen. The elements that make up compounds are always present in definite amounts.

Properties of compounds The properties of compounds are usually totally different from the properties of the elements from which they are made. Sodium (a reactive metal) + = Table Salt Chlorine (a poisonous gas)

TextbookChapter22-Elements,CompoundsandMixtures A1. Atom. A2. Element. A3. Compound. A4. Molecule. A5. Molecule,atoms,atom. A6. CO2,atom,atoms. A7. Molecule,element,compound.

A8. Hydrogen atoms, nitrogen atoms. A9. New properties. A10. Mixture, substances, mingled, chemically combined. A11. New. A12. Salt, water, steel. A13. Mixture, nitrogen,oxygen,water. A14. Water. A15. Mixture, magnet. A16. Compound, iron sulfide

B1. (a) An atom is the smallest part of an element that still has the properties of that element. (b) An element is a substance that cannot be broken down into simpler substances by chemical means . (c) A compound is formed when two or more elements combine chemically. (d) A molecule is the smallest part of an element or compound that can exist on its own. (e) A mixture consists of two or more different substances mingled together but not chemically combined.

B2. H, C, Cu, S, Fe, N, Zn, Al, Na, Cl, Ag, Au. B3. (a)neon, (b)iron, (c)gold, (d)aluminium, (e)copper, (f)mercury, (g)carbon, (h)lead, (i)oxygen, (j)fluorine, (k)chlorine, (l)helium.