Atoms and the periodic table

1. Atoms and the periodic table Non metals and Metalloids

2. A non metal is an element that is not a metal and does not have properties of metals • A metalloid is an element that is not a metal but it is similar to a metal. • Physical properties of nonmetals: Most nonmetals are poor conductors of electric current and heat. Solid nonmetals tend to be dull and brittle. • Brittle: breaks or crumbles into a powder when struck with a heavy object.

3. Page 333 look at figure 1. • What is true about all the elements that make up DNA? They are nonmetals • How does the number of phosphorous atoms compare to the number of hydrogen atoms? There are fewer phosphorous atoms. • What other compounds can you name that are made of some of the elements in DNA? WATER,CARBON DIOXIDE • Can you think of other substances essential to life that contain nonmetals? Water,air.

4. Non metals usually have lower densities than metals. • In terms of chemical properties atoms of nonmetals usually gain or share electrons when they react with other atoms. • An example of gain is when sodium and chlorine react to form table salt(NaCl).An electron moves from the sodium atom to the chlorine atom. • An example of sharing is when two or more atoms bond to form a molecule. Nonmetals forming compounds with other nonmetals: a water molecule consisting of two hydrogen atoms and one oxygen atom.

5. Page 334 “apply it “ .Compare and contrast properties of metals with properties of non metals.

6. In the periodic table there are families(groups) that contain nonmetals. • Families containing nonmetals include the carbon family (group 14), the nitrogen family( group 15), the oxygen family ( group 16), the halogen family (group 17), the noble gases( group 18), and hydrogen in group 1. • What is true about groups 1,14,15,16,17? They are mixed groups. • What is different about group 18? It contains only metals. • What gives groups 14,15,16 their names? The first element in the family which is nonmetal.

7. What properties do elements in mixed groups share? They all gain, lose or share the same number of electrons. • Which group contains elements that don not react under normal conditions? Group 18, the noble gases. • Which nonmetal is found in group 1? Hydrogen.

8. In group 14, Carbon is the only element that is nonmetal. Carbon is very important in the chemistry of life. Proteins, carbohydrates, DNA, fats, all contain carbon. Fuels, coal, gasoline all contain carbon. A diamond is made of pure carbon. • Page 335 complete the table about families containing nonmetals.

9. In group 15 the nitrogen family contains two nonmetals-nitrogen and phosphorus. • Nitrogen makes up about 78% of Earth’s atmosphere. • In nature nitrogen exists as two nitrogen atoms bonded together to form a diatomic molecule. • A diatomic molecule is made up of two atoms. • Nitrogen is not very reactive. Phosphorus, the other nonmetal in the family, is much more reactive than nitrogen. Phosphorus is always found in compounds.

10. Group 16,the oxygen family, contains three nonmetals: oxygen, sulfur and selenium. • Oxygen is gas at room temperature, sulfur and selenium are both solids. • Oxygen is a diatomic molecule and is relatively reactive so it can combine with almost every other element. • Smell of a rotten egg, is the smell of a sulfur compound. Sulfur is used in manufacturing of rubber, rubber bands, car tires.

11. Group 17 nonmetals include fluorine ( F) , chlorine (Cl), bromine (Br), and iodine ( I). • These elements are also known as the halogens- it means “salt forming”. • All halogens are very reactive. Fluorine is the most reactive. It reacts with almost every known substance. • Chlorine gas is dangerous but it is used in small quantities to kill water bacteria. • Halogen elements may be dangerous but they are useful. Compounds of fluorine make up the non stick coating of cookware. It is also found in toothpaste because it prevents tooth decay.

12. Group 18 has elements known as noble gases. • They do not form compounds because atoms of noble gases do not usually gain, share or lose electrons. • As a result they are usually nonreactive. • Alone in group 1 is hydrogen. It is the element with the simplest atoms. • Hydrogen makes up more than 90% of the atoms in the Universe. • Stars contain massive amounts of hydrogen(the sun). • Hydrogen makes up only 1% of the Earth’s oceans and atmosphere. Most hydrogen is combined with oxygen in water.

13. Metalloids: elements that have some properties of metals and some of nonmetals. • All metalloids are solid at room temperature and are brittle, hard and somewhat reactive. • Most common metalloid is silicon. Ordinary sand(silicon dioxide) is the main component of glass. • Metalloids most useful property is the ability to conduct electric current. • Metalloids such as silicon and germanium(Ge) are used to make semiconductors. • Semiconductors are substances that can conduct electric current under some conditions. Semiconductors are used to make computer chips, transistors, lasers and in solar cells.