Lecture 5 6/27

Today’s Agenda Metals and Nonmetals Periodic Table – Periods – Groups – Blocks Valence Electrons. – Bond formation. Periodic Trends.

Metals and Nonmetals Metals: – Have luster – Are malleable and ductile – Conduct heat and electricity – Tend to lose electrons Found on the left and center of the periodic table.

Metals and Nonmetals Nonmetals: – Are dull – Are brittle – Tend to gain electrons – Do not conduct heat or electricity very well Found on the right side of the periodic table. Can be a gas, liquid, or solid.

Metalloids Substances that contain properties of both metals and nonmetals – They are semiconductors! Some metalloids lean more towards one side though. Aluminum is almost all metal whereas Boron is almost all nonmetal. They exist on the “staircase” line.

The Periodic Table The Rows are called Periods. – They correspond to energy levels an electron can be in. The Columns are called Groups. – Elements in groups have very similar properties. – This is due to the same number of electrons and a bit more complicated things. There are 4 blocks in the periodic table. – s, d, p, and f.

The Periodic Table Alkali Metals: – Group 1 – Extremely reactive and therefore, they each lose one electron very easily. Alkali Earth Metals: – Group 2 – Also very reactive and therefore, they each lose 2 electrons very easily.

The Periodic Table Halogens: – The most reactive elements – Group 7 – Not all of them are gases! Noble gases: – Inert (generally do not react with anything) – Group 8 – They are extremely stable

The Periodic Table Blocks: There are 4 blocks on the periodic table: – s block, which is the first two groups, including helium. – d block, which contains the transition metals. – p block, which contains the nonmetals, metalloids, and a couple metals. – f block, which is at the bottom, and known as the inner transition elements.

Valence Electrons Valence Electrons exist in the outermost energy level of the atom or ion. These are the electrons involved in bonding. Octet Rule: – An atom or ion cannot contain more than 8 electrons. As we will see soon, the electrons that a metal donates is accepted by a nonmetal to form a bond.

Valence Electrons Atoms strive to have a stable electron configuration (having none or all eight). – Another example in Chemistry of things striving to become more stable (with lower energy). – This is why the noble gases are inert (unreactive). Noble gases are stable because the entire outer energy level is filled with electrons. – They are very stable.

Periodic Trends Electronegativity: – The craving for an electron. – As you go across a period from left to right it increases. – As you go down a group, it decreases. – The maximum number is 4, and it is assigned to fluorine, the most electronegative element.

Periodic Trends Atomic radius – The length between the nucleus and the outside of the atom. – Going across a period, it decreases. – Going down a group, it increases. – It all has to do with attraction between protons and electrons. – Shielding occurs when going down a group.

Ionization Energy The energy required to remove an electron from an atom. – Thereby making a positively charged ion. – As you move across a period, ionization energy increases. – As you move down a group, ionization energy decreases. – The first ionization energy is always lower than the second. Why?

Next Class Print off lab 3 and read by Friday EXAM 1!!!!!!!!!!!!! Homework 5 due. Lab 2 is due Friday.