Periods, groups, and trends The Periodic Table Periods, groups, and trends

The Bohr Model After Rutherford’s model of the atom, Neils Bohr created our modern atomic model He suggested that the electrons of an element are arranged in energy levels or “energy shells” Using this model helps us understand the periodic table of elements

What is The Periodic Table of Elements? An arrangement of the elements

Periodic Law “When the elements are arranged according to their atomic numbers, elements with similar properties appear at regular intervals” When elements are arranged by their atomic numbers, groups of elements begin to have similar characteristics

Organization of the Periodic Table Elements in each column of the periodic table have the same number of electrons in their outer shell Called “valence electrons” Elements with the same number of valence electrons react in similar ways

Periods A horizontal row on the periodic table of elements is called a period

Groups A vertical column of the periodic table is called a group Elements in a group share similar chemical properties

Main Group Elements Elements in groups 1,2, and 13-18 are known as main group elements Electron configurations of each element are regular and consistent Main group elements include: Alkali Metals Alkaline Earth Metals Halogens Noble Gases

Alkali Metals – Group 1

Alkali Metals – Group 1 They are metals that react with water They are very reactive Never found in nature as “pure elements” but are found as compounds Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium

Alkaline Earth Metals – Group 2

Alkaline Earth Metals – Group 2 Slightly less reactive than Alkali Metals Have 2 valence electrons

Halogens – Group 17

Halogens– Group 17 The most reactive group of the non metal elements They have 8 valence electrons React with most metals to produce salts Sodium and Chlorine – Table Salt

Noble Gases – Group 18

Noble Gases – Group 18 Group 18 elements are called Noble Gases Have a very low reactivity

Hydrogen The most common element in the universe It only has one proton and one electron so it is unlike any other element Reacts with many other elements

Transition Metals These occupy the center of the periodic table

Transition Metals cont. Extremely unreactive Some almost never form compounds with other elements

Metals All Metals are excellent conductors of electricity Most often distinguishes metals from non-metals Can be brittle or malleable

Metalloids Found on the table between metals and non metals

Metalloids All metalloids are solids at room temperature Have some characteristics of metals and have some characteristics of non-metals

Non-Metals Many non-metals are gases at room temperature Poor conductor of heat and electricity Found on the right side of the periodic table

Periodic Trends The arrangement of the periodic table reveals trends in the properties of the elements A trend is a predictable change or characteristic Understanding a trend among elements in a group or period enables you to make predictions about their behavior

Ionization Energy Ionization energy is the energy required to remove an electron from an atom

Ionization Energy Cont. Ionization energy decreases as you move down a group

Ionization Energy cont. Ionization energy increases as you move from left to right across a period

Melting Point Metals generally posses a high melting point Most nonmetals possess low melting points

Electronegativity Refers to how strongly each atom attracts other electrons An atom with higher electronegativity will pull on the electrons more strongly than another atom will Electronegativity decreases as you move down a group Electronegativity increases from left to right across a period