Chapter 5 The periodic table

Our periodic table is arranged by order of increasing atomic number. This is called the periodic law

Arrangements The rows that go ACROSS the table are called periods.

Look all the elements in periods 2 do they have anything is common? What about all the elements in period 3?

All elements in the same period have the same number of electron levels! Period 1 all has 1 electron level Period 2 all has 2 electron levels Period 3 all has 3 electron levels Period 4 all has 4 electron levels

Look at all the elements in period 3…. What do you see do they all have different?

All elements in the period increase by 1 proton (Atomic number) as we go across. They also gain 1 electron as we go across.

Groups The rows that go up and down are called groups (or families).

Look at all the elements in group 2 what do they all have in common?

Groups (almost) All elements in the same group have the same number of valence electrons. And since the number of valence electrons determines the way an element reacts, atoms in the same group react the same way!!!!

Types of elements There are 3 different types of elements Metals, Non metals and metalloids (in between)

Metals Metals are solid at room temperature (except mercury Hg) Metals are malleable- they can be bent into shapes. Metals have luster (they are shiny) They are good conducters of heat and electricity.

metals Metals lose electrons easily (more on this later) and they have low electro negativity.

Nonmetals Most nonmetals are either gas or solid at room temperature (except bromine which is a liquid) They are not malleable or ductile They are lack luster They are poor conductors of electricity or heat

Nonmetals Nonmetals tend to gain electrons (more on this later) And have a high electro negativity.

Allotropes Sometimes certain non metals can be found in nature in different natural forms. Oxygen is found naturally as either O 2 or O 3 (ozone) Carbon can be found naturally as diamonds or graphite

These forms are called Allotropes. Allotropes are when one elements can have more then 1 natural form in nature. Allotropes are totally different from each other physically and chemically.

Metalloids Metalloids are elements that have some aspects of metals and some aspects of non metals. These elements are found touching the Zigzag line.

Trends Look up the EN and Ionization energy in of all elements in period 3. Do you see a pattern emerge as you move across the table?

Trends in EN As we go across the table the elements hold their electrons tighter (Higher EN and Ionization E). This is because they have more protons to attract the electrons.

EN in a group Now look up all the EN and Ionization energies down group 2… Do you see a pattern?

EN in groups As we go down a group the attraction for electrons get weaker. (lower EN & ionization energy). This is because the electrons move farther and farther away from the nucleus, so they are not as attracted.

going across EN & Ionization E go up going down EN & Ionization E go down

Since as we go across the table we go from metals to non metal…. As we go across the metallic properties increase.

Atomic Radius Each different element has atoms that are a different size. Look up the atomic radius for group 2 and period 2. What is the trend?

Properties of groups Group one is called the Alkali metals Group two is called the Alkaline earth metals These metals lose electrons easily & become more reactive as we move down the group

Group 17 Group 17 is known as the halogens. It is the only group to have elements that exist in all phases at room temp Fluorine & chloride are gasses Bromine is a liquid Iodine is a solid.

Group 18 Group 18 is called the noble gasses. They are always found as a gas and ALMOST NEVER react. This is because it has a full set of valence electrons (more on this later) They are also called the inert gasses.

Reactions between groups Look at the oxidation numbers in elements in group 1 and 17. What do you see.

1 & 17 Since group 1 elements gain a +1 charge and group 17 have a -1 charge they usually react in a 1:1 ratio. ex, NaCl ex, NaClLiFKClNaBr

2 & 16 Look at the oxidation numbers of group 2 and 16 what do you see?

2 & 16 Since group 2 usually has a +2 charge and group 16 has a minus 1 charge they usually react in a 1:1 ratio Ex: MgO BeSCaO

2 & 17 Look at group 2 and 17 what ratio will they react in?

2 & 17 Since group 2 has a +2 and group 17 has a -1 they usually have a 1:2 ratio Ex. BeCl 2 MgBr 2 CaF 2