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Atoms are arranged in the periodic table by atomic number Starting from left to right

An element’s identity is controlled by the number of protons An element’s chemical behavior and reactivity is controlled by the number of electrons and their placement in energy levels within the electron cloud that surrounds the nucleus

The energy levels for electrons in the electron cloud are called shells. Each shell can hold up to a certain number of electrons. 1 st shell holds up to 2 2 nd shell holds up to 8 3 rd shell holds up to 18

Periods Each row is called a “period” The elements in each period have the same number of shells

Groups Each column is called a “group” Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons The electrons in the outer shell are called “valence electrons”

Transition Metals Transition Metals have slightly different rules for shells and valence electrons. This is something you will learn about in High School Chemistry.

Determine the number of shells and the number of valence electrons for:

Determine the number of shells and the number of valence electrons for:

Helium is the exception in Group 8. Since it has just one shell, that shell can only fit 2 electrons instead of 8. It is in this group because all the elements have a full outer shell.

How to Draw Lewis Structures

Lewis Structures 1) Find your element on the periodic table. 2) Determine the number of valence electrons. 3) This is how many electrons you will draw.

Lewis Structures Find out which group (column) your element is in. This will tell you the number of valence electrons your element has. You will only draw the valence electrons.

Groups - Review Each column is called a “group” Each element in a group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons The electrons in the outer shell are called “valence electrons”

Lewis Structures 1) Write the element symbol. 2) Carbon is in the 4 th group, so it has 4 valence electrons. 3) Starting at the right, draw 4 electrons, or dots, counter- clockwise around the element symbol.

Lewis Structures 1) Check your work. 2) Using your periodic table, check that Carbon is in the 4 th group. 3) You should have 4 total electrons, or dots, drawn in for Carbon.

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Lewis Structures On your worksheet, try these elements on your own: a)H b)P c)Ca d)Ar e)Cl f)Al

Metals, Nonmetals, & Metalloids On many periodic tables, a jagged black line (see next slide) along the right side of the table separates the metals from the nonmetals. Metals are to the left of the line (except for hydrogen, which is a nonmetal) Nonmetals are to the right of the line, and Metalloids are the elements immediately adjacent to the line.

Metals, Nonmetals, & Metalloids