What determines an element’s chemistry

When atoms combine they form compounds. Electrons of an atom are found in different energy levels. Valence electrons are the outermost electrons in an atom.They have higher amounts of energy Valence electrons in an atom determine the element’s chemical properties. The term “valence” comes from the Latin word valentia, meaning power.

How many electrons are in a neutral atom? The same number as the number of protons. How are an atom’s valence electrons different from the rest of the atom’s electrons? The valence electrons have the highest energy. Why are valance electrons important? They are involved in forming chemical bonds What is a chemical bond? The force of attraction that holds two atoms together as a result of the arrangement of electrons between them. Valence electrons in an atom. The outermost electrons, are represented by an electron dot diagram. See figure 1,page 359. How many valence electron Hydrogen has? Carbon? Oxygen?

Applying the periodic table The elements in the periodic table are in order by increasing atomic number The number of valence electrons increases from left to right across each period. Each period begins with an element that has 1 valence electron and ends with an element that has 8 valence electrons.(Period 1 is the exception ending with Helium which has 2 valence electrons). Thus, group 1 elements ( alkali metals) have 1 valence electron. Group 2 elements ( alkaline earth metals) have 2 valence electrons. Group 3 –group 12 (transition metals) is an exception to the rule and uses the “d electron count method” an electronic configuration. Group 13 elements have 3 valence electrons. Group 14 elements (Carbon family) have 4 valence electrons; Group 15 elements (nitrogen family) have five valence electrons; Group 16 elements (oxygen family ) have six valence electrons. Group 17 elements (halogens) have 7 valence electrons. Group 18 elements(noble gases) have 8 valence electrons. Look figure 2,page 360 periodic table of elements.

An important distinction between metals and non metals is how their valence electrons form bonds. Metals lose electrons when they bond with other atoms. The reactivity of a metal depends on how easily its atoms lose valence electrons. Nonmetals become stable when they gain or share enough electrons to have 8 valence electrons.

Metalloids have some properties of metals and some properties of nonmetals. When metalloids combine with other elements what happens to their valence electrons? They either lose or share them How is this similar to metals? Metals lose electrons when they combine with other elements. How is this different from metals? Metals do not share electrons.