Review… Here are three isotopes of an element: 612C 613C 614C The element is: __________________ The number 6 refers to the _________________________ The numbers 12, 13, and 14 refer to the ________________________ How many protons and neutrons are in the first isotope? _________________ How many protons and neutrons are in the second isotope? _________________ How many protons and neutrons are in the third isotope? _________________

Naturally occurring europium (Eu) consists of two isotopes was a mass of 151 and 153. Europium-151 has an abundance of 48.03% and Europium-153 has an abundance of 51.97%. What is the atomic mass of europium?

Periodic Trends Chapter 6

Dmitri Mendeleev In 1871, Russian Dmitri Mendeleev organized the known elements according to increasing atomic mass. Left spaces on the table where elements were yet to be discovered. He recognized similarities in the chemical properties of elements occurring at regular intervals.

Henry Moseley In 1913, British physicist who discovered that the elements fit into patterns better when they are arranged in order of increasing atomic number. Periodic Law- the physical and chemical properties of the elements are periodic functions of their atomic numbers.

How are Elements Classified? Elements can be classified as metals, nonmetals, or metalloids. Metals Nonmetals Metalloids (semimetals) Good conductor of heat and current High luster Solid at room temp Most are malleable Poor conductor of heat and current Most are gases at room temp If solid they are brittle Some conditions behave like a metal, some a nonmetal

Let’s take a look at pg 168 in the textbook

Atom Size The atomic radius is one-half of the distance between the nuclei of two atoms of the same element when the atoms are joined. Increases from top  bottom Decreases from left  right

Summary of Atomic Radius

Ions An atom or group of atoms that has a positive or negative charge. Positive and negative ions form when electrons are transferred between atoms. Atoms of metals tend to form ions by losing one or more electrons from their highest occupied energy levels.

Ionization Energy Electrons move to higher energy levels when excited. Sometimes the electron has enough energy to overcome the attraction of the protons in the nucleus. The energy required to remove an electron from an atom is called ionization energy. Ionization energy decreases from top to bottom and increases from left to right.

Summary of Ionization Energy

Electronegativity Electronegativity can be used to predict the type of bond that will form during a reaction. The ability of an atom to attract electrons when the atom is in a compound. Decrease from top to bottom, increases from left to right. Fluorine has the highest electronegativity.