CP- L 1.7 Valence Electrons and Reactivity

CP- L 1.7 Valence Electrons and Reactivity

By Ms. Bailey*

​Lesson Objectives:

​KWBAT explain how valence electrons determine an element’s chemical reactivity.

​TEKs:​

​8.5(B):  identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity

Open Ended

What are valence electrons?

SS: Valence electrons are....

Recall that valence electrons  are the outermost electrons.  These electrons can participate in interactions with other atoms and determine an element’s chemical properties; elements with the same number of valence electrons have similar chemical properties.

​

​Some text here about the topic of discussion.

Open Ended

Based on the text and figures on the last slide, what are examples of elements that have just one valence electron?

SS: Three elements that have only one valence electron are...

Open Ended

How many valence electrons does oxygen (O) have?

SS: Oxygen has___ valence electrons.

Open Ended

How many valence electrons do elements in group fourteen have?

SS: Elements in group fourteen have___ valence electrons.

​Chemical reactivity is the capacity of an atom to participate in a chemical reaction.  Chemical reactivity is directly related to the number of valence electrons.  Atoms are typically stable or non-reactive when they have a full outer electron shell.  For almost all atoms, except hydrogen and helium, a full outer electron shell means the atom has eight valence electrons. Atoms that have 8 valence electrons are said to follow the “octet rule.”  The word “octet” means 8.  For example, an octagon has 8 sides or an octopus has 8 legs. Elements that follow the octet rule have 8 valence electrons.   Hydrogen and helium are stable when they have two valence electrons.

Generally, elements with only one outermost valence electron are more reactive than elements that have a stable outermost shell with eight electrons.  Additionally, elements with seven valence electrons are more reactive than elements that have eight valence electrons. The noble gases in group 18 have a completely filled outer electron shell, so they have little chemical reactivity.  Group 1 metals are highly reactive as with the case for sodium that reacts immediately, bursting into flames, when it comes into contact with water.

Open Ended

Why are elements in group 18 the least reactive?

SS: Elements in group eighteen are least reactive because....

Multiple Choice

High, medium or low reactivity....

Lithium ( Li)

• High

• Medium

• Low

Multiple Choice

High, medium or low reactivity....

Carbon (C)

• High

• Medium

• Low

Multiple Choice

High, medium or low reactivity....

Krypton (Kr)

• High

• medium

• Low

Multiple Choice

High, medium or low reactivity....

Tin (Sn)

• High

• Medium

• Low

​Exit Ticket Time!

Multiple Choice

The atoms of a certain element each contain 11 protons and 1 valence electron.  Which statement correctly identifies this element and describes its chemical reactivity?

• The element is sodium, and it is highly reactive.

• The element is fluorine, and it is not very reactive.

• The element is sodium, and it is not very reactive.

• The element is fluorine, and it is highly reactive.

Multiple Choice

A student is studying calcium, a highly reactive element that humans need for strong bones.  Which characteristic of calcium is most closely related to its chemical reactivity?

• The 20 protons in each atom of calcium

• The density of calcium, which is 1.54 g/cm3

• The atomic mass of calcium, which is 40.078 amu

• The 2 valence electrons in each atom of calcium

Multiple Choice

The atoms of a certain element each contain 10 protons and 8 valence electrons.  Which statement correctly identifies this element and describes its chemical reactivity?

• The element is chlorine, and it is not very reactive.

• The element is neon, and it is not very reactive.

• The element is chlorine, and it is highly reactive.

• The element is neon, and it is highly reactive.

Multiple Choice

Magnesium, Mg is a silvery white metal.  It has a high melting and boiling point compared to other elements and is widely used by scientists in medicine to treat skin related problems. Which statement correctly describes atoms of magnesium?

• Magnesium has 25 protons and is relatively reactive.

• Magnesium has 25 protons and is not reactive.

• Magnesium has 12 protons and is relatively reactive.

• Magnesium has 12 protons and is not reactive.

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