Objectives Be able to define atomic number and atomic mass. Be able to use the periodic table to determine the number of protons, electrons, and neutrons in an atom. Be able to describe the structure and groupings of the periodic table.

Here are the basics; you need to know these. Atomic Structure Here are the basics; you need to know these. 1 H 1.0076 Hydrogen Atomic Number: the number of protons (p+) Atomic Mass: the number of protons (p+) + the number of neutrons (n0) ▪ measured in atomic mass units (amu) which is one twelfth the mass of a carbon-12 atom. ▪ the mass of electrons (1/1860 p+) is negligible. Number of Neutrons: the atomic mass - the atomic number Atomic Number Atomic Symbol Atomic Mass

Element Atomic Number # Protons # Electrons Atomic Mass # Neutrons

Development of the Periodic Table The modern periodic table of elements is mostly the work of Russian chemist Dmitri Mendeleev (1834-1907). It was set up in such a way so group elements in columns according to their properties, but also put them in ascending order according to their atomic number. Let’s observe: The vertical columns are called groups; the horizontal rows are called periods. Periodic Law: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical & chemical properties.

Groups The vertical columns are called groups, or families. There are 18 groups on the periodic table. Groups

The horizontal rows are called periods. Periodic Law: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical & chemical properties.

Elements in the same group: physically and chemically similar Periodic Trends Elements in the same group: physically and chemically similar Elements in the same period: ordered in increasing size and atomic number.

Francium is the most active metal. Metals Characteristics of metals: excellent conductors of heat and electricity, very reactive, usually make positive ions when dissolved in solution, mix well to make alloys. Francium is the most active metal.

Group 1A: Li, Na, K, Rb, Cs, Fr Does not include hydrogen Alkali Metals Group 1A: Li, Na, K, Rb, Cs, Fr Does not include hydrogen ▪ They are very reactive because of the lone electron in their outer shell. ▪ React vigorously, even explosively with water *Very shiny and light in weight Arabic – “ashes” Ashes and water: Slippery for removing grease (soaps)

Alkali Earth Metals Group 2A: Be, Mg, Ca, Sr, Ba, Ra ▪ Not as reactive as alkali metals, but form bonds very easily. Same as alkali Group 1 but also fire-resistant

Groups 3-12 are harder than alkali metals. Transition Metals Groups 3-12 are harder than alkali metals. Have a special electron shell arrangement where two of their outer shells are not full. This allows them to bond to many other elements in a variety of shapes.

Chalcogens Group 16 “ore-forming” (Greek) Oxygen and sulfur are commonly found in ore

with metals to form salts. When an halogen Halogens Have an outer shell that is almost full, therefore very reactive. Often bond with metals to form salts. When an halogen combines with another element, the resulting compound is called a halide. “salt forming” Halogen lamp has small amounts of iodine or bromine (glow brighter without burning out so quickly)

Inert Gases (Noble gases) Include: He, Ne, Ar, Kr, Xe, Rn. Have a full outer shell and are very unreactive, hence the title “inert”.

· Also known as rare-earth or inner-transition elements. Lanthanide Series · Also known as rare-earth or inner-transition elements. · Fifteen elements that start with lanthanum (La) at atomic number 57 and finishing up with lutetium (Lu) at number 71

some elements with higher numbers have only been made in labs. Actinide Series · These elements are all radioactive and only some are found in nature; some elements with higher numbers have only been made in labs. ·Fifteen elements that start with actinium (Ac) at atomic number 89 and finishing up with lawrencium (Lr) at number 103

Metalloids are found on the periodic table between the metals and non-metals. Appropriately, they exhibit characteristics of both metals and non-metals. Several of the metalloids are electrical semiconductors (circuits and computer chips). Find the metalloids Boron, silicon, germanium, arsenic, selenium, antimony, tellerium, polonium, astatine

Nonmetals Flourine is the most active nonmetal. Many nonmetals are gases at room temperature: N; O; F; Cl Flourine is the most active nonmetal. These are elements that are poor conductors of heat and electricity.