Introduction to Atoms and the Periodic Table Section 1 – Atomic Structure

Atoms are the building blocks of all matter. Atoms are the building blocks of all matter. Atoms are the smallest units of matter.Atoms are the smallest units of matter. Atoms are made of protons, neutrons, and electrons.Atoms are made of protons, neutrons, and electrons. Definition: proton – an atomic particle with a positive charge.Definition: proton – an atomic particle with a positive charge. Definition: neutron – an atomic particle with a neutral charge.Definition: neutron – an atomic particle with a neutral charge. Definition: electron – an atomic particle with a negative charge.Definition: electron – an atomic particle with a negative charge.

Definition: nucleus – the core of an atom that is composed of protons and neutrons. Definition: nucleus – the core of an atom that is composed of protons and neutrons. The nucleus of an atom is held together by strong nuclear force. The nucleus of an atom is held together by strong nuclear force.

The electrons of an atom are found outside the nucleus in orbitals. The electrons of an atom are found outside the nucleus in orbitals. Inside the orbitals, the electrons exist in different energy levels.Inside the orbitals, the electrons exist in different energy levels. There are 4 energy levels, with Level 1 being the lowest level.There are 4 energy levels, with Level 1 being the lowest level. Each energy can hold only a certain number of electrons. Each energy can hold only a certain number of electrons.

Energy Level 1 holds 2 electrons. Energy Level 1 holds 2 electrons. Energy Level 2 holds 8 electrons. Energy Level 2 holds 8 electrons. Energy Level 3 holds 18 electrons. Energy Level 3 holds 18 electrons. Energy Level 4 holds 32 electrons. Energy Level 4 holds 32 electrons.

For example. Oxygen has 8 electrons. 2 of them fit into energy level 1, and the other 6 can fit into energy level 2.For example. Oxygen has 8 electrons. 2 of them fit into energy level 1, and the other 6 can fit into energy level 2. The “left-over” electrons in the outermost energy level are very special. These electrons are called valence electrons.The “left-over” electrons in the outermost energy level are very special. These electrons are called valence electrons. Definition: valence electron – an electron found in the outermost energy level of an atom. Valence electrons determine an atom’s chemical properties!Definition: valence electron – an electron found in the outermost energy level of an atom. Valence electrons determine an atom’s chemical properties!

Chapter 4: Atoms and the Periodic Table Section 2 – The Periodic Table

All of the known elements in the universe are arranged according to their properties. All of the known elements in the universe are arranged according to their properties. The periodic table lists each element known.The periodic table lists each element known. Elements in the table are arranged into groups and periods.Elements in the table are arranged into groups and periods. Definition: group – a vertical column of elements on the periodic table.Definition: group – a vertical column of elements on the periodic table. Definition: period – a horizontal row of elements on the periodic table.Definition: period – a horizontal row of elements on the periodic table. Notice that the atomic number of elements increases by 1 from left to right across the table.Notice that the atomic number of elements increases by 1 from left to right across the table.

PERIODS Horizontal rows Horizontal rows number of protons & electrons increases as you move from left to right number of protons & electrons increases as you move from left to right

GROUP/FAMILY vertical column of elements vertical column of elements Atoms of elements in same group have same number of valence electrons Atoms of elements in same group have same number of valence electrons elements have similar properties elements have similar properties

The groups and periods have other sequences and similarities. The groups and periods have other sequences and similarities. Look at the group number of Calcium. It is in group 2. It also has 2 valence electrons.Look at the group number of Calcium. It is in group 2. It also has 2 valence electrons. Fluorine is in group 17. It has 7 valence electrons.Fluorine is in group 17. It has 7 valence electrons. So…a quick and easy way to figure out the number of valence electrons is to look at the group number of the element.So…a quick and easy way to figure out the number of valence electrons is to look at the group number of the element. If the element is in groups 11-18, look at the second digit.If the element is in groups 11-18, look at the second digit.

Another trend that we see in the periodic table is a change in the size of the atomic radius. Another trend that we see in the periodic table is a change in the size of the atomic radius. As you move from left to right across the periodic table, atomic radius decreases. (except for the elements in group 18)As you move from left to right across the periodic table, atomic radius decreases. (except for the elements in group 18) As you move down a group the radius generally increases.As you move down a group the radius generally increases.  What element has the smallest atomic radius?  What element has the largest atomic radius?

Chapter 4: Atoms and the Periodic Table Section 1- How to use the periodic table

Isotopes Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. Example: Carbon-12 has 12 protons and 12 neutrons. Carbon-13 has 12 protons and 13 neutrons.Example: Carbon-12 has 12 protons and 12 neutrons. Carbon-13 has 12 protons and 13 neutrons. They are identified by their mass number.They are identified by their mass number.

Atomic Mass(A) It is the weighted average of the isotopes. It is the weighted average of the isotopes. You can use this number (round it up to a whole number) or mass number to calculate the number of neutrons in an atom by subtracting the atomic number from it. You can use this number (round it up to a whole number) or mass number to calculate the number of neutrons in an atom by subtracting the atomic number from it.

ATOMIC NUMBER (Z) Number of protons in the nucleus Number of protons in the nucleus The number of protons are equal to the number of electrons in a neutral atom. The number of protons are equal to the number of electrons in a neutral atom. The atomic number never changes. The atomic number never changes.

Chapter 4: Atoms and the Periodic Table Section 2 – Families of Elements

METALS NONMETALS

We already know that elements are arranged into groups and periods, but there is also a method of arranging the elements according to their properties. We already know that elements are arranged into groups and periods, but there is also a method of arranging the elements according to their properties. There are 3 major categories of elements: Metals, Nonmetals, and Metalloid. There are 3 major categories of elements: Metals, Nonmetals, and Metalloid.

Metals Metals: There are different families of metals. Metals are on the Left side of the periodic table. (Not Hydrogen)Metals: There are different families of metals. Metals are on the Left side of the periodic table. (Not Hydrogen) 1. Alkali Metals – elements in group 1, and are extremely reactive. 2. Alkaline-Earth metals – elements in group 2 that are very reactive. 3. Transition Metals – elements in the middle, groups 3-12 on the periodic table. 1.Gold, Silver, Iron, and many other familiar metals are classified as Transition Metals.

Metals Most of the elements are metals Metals are good conductors of electricity and heat. Shiny appearance, are ductile, malleable, and are solid at room temperature. A mixture of two or more metals is called an alloy.

Nonmetals are found on the upper right side of the periodic table, plus hydrogen. Nonmetals are found on the upper right side of the periodic table, plus hydrogen. Halogens – elements in group 17 of the periodic table. Halogens are extremely reactive elements. Halogens – elements in group 17 of the periodic table. Halogens are extremely reactive elements. Noble Gases – elements in group 18 of the periodic table. Noble Gases are inert, which means nonreactive. Noble Gases – elements in group 18 of the periodic table. Noble Gases are inert, which means nonreactive. Nonmetals

Nonmetals Generally gases or dull brittle solids Generally gases or dull brittle solids Poor conductors of heat and electricity. Poor conductors of heat and electricity.

These elements have properties of Metals & Nonmetals. These elements have properties of Metals & Nonmetals. Can be found in a stair case pattern in Groups Can be found in a stair case pattern in Groups Metalloids