Chem Unit 6

Groups/Families

Columns on the period table

Periods

rows on the periodic table, as you move left to right across a period the elements get more nonmetallic from very metallic

Metals

elements with high melting points, usually solid, good conductors, malleable, ductile, usually shiny

Nometals

elements that are “opposite” from metals, poor conductors, most are gas at room temp

Metalloids

combined features of nonmetal and metalloids

Mendeleev’s Periodic Table

elements were arranged in order of increasing mass

periodic table

today’s periodic table increases by atomic number

Periodic law

when arranged in oder of increasing atomic number, there will be a periodic repetition of properties

Alkali Metals

Group IA, very reactive metals

Alkaline Earth Metals

Group 2A, also reactive

Halogens

Group 17A, nonmetals

Noble Gases

Group 8A, not reactive, have perfect octet

Representative elements

Groups 1A through 7A because they display a wide range of properties

Atomic Radius

half of the distance between the nuclei of two atoms of the same element when they are joined

Atomic size

increases from top to bottom in a group and decreases from left to right across a period

shielding

nuclear charge is smaller when the element’s atoms are bigger with lots of electrons on higher energy levels are farther and blocked by electrons closer to the nucleus

Positive/negative ions

occur when electrons transfer between atoms

cation

ion with a positive charge, means that it lost an electron, smaller

anion

ion with negative charge, means it gained an electron, bigger

ionization energy

the energy required to remove an electron from an atom

first ionization energy

tends to decrease from top to bottom within a group and increase across a period

trend in reactions between metals and nonmetals

metal usually loses electrons, nonmetals tend to gain electrons

electronegativity

ability of an atom of an element to attract electrons, values decrease from top to bottom in a group, for REPRESENTATIVE ELEMENTS the values tend to increase from left to right across a period