Question

Determine the number of valence electrons in an atom of each of the following elements: a. \(\mathrm{H}\) b. \(\mathrm{F}\) c. \(\mathrm{Mg}\) d. \(\mathrm{0}\) e. \(\mathrm{Al}\) f. \(\mathrm{N}\) g. \(\mathrm{C}\)

Short answer

H: 1, F: 7, Mg: 2, O: 6, Al: 3, N: 5, C: 4

Step-by-step solution

Define Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom. They determine how an element reacts chemically.

Look Up Each Element's Group on the Periodic Table

Each element belongs to a specific group in the periodic table, and this group number typically indicates the number of valence electrons for the element (for Groups 1-2 and 13-18).

Determine Valence Electrons for Hydrogen (\text{H})

Hydrogen is in Group 1 of the periodic table. Therefore, it has 1 valence electron.

Determine Valence Electrons for Fluorine (\text{F})

Fluorine is in Group 17 of the periodic table. Therefore, it has 7 valence electrons.

Determine Valence Electrons for Magnesium (\text{Mg})

Magnesium is in Group 2 of the periodic table. Therefore, it has 2 valence electrons.

Determine Valence Electrons for Oxygen (\text{O})

Oxygen is in Group 16 of the periodic table. Therefore, it has 6 valence electrons.

Determine Valence Electrons for Aluminum (\text{Al})

Aluminum is in Group 13 of the periodic table. Therefore, it has 3 valence electrons.

Determine Valence Electrons for Nitrogen (\text{N})

Nitrogen is in Group 15 of the periodic table. Therefore, it has 5 valence electrons.

Determine Valence Electrons for Carbon (\text{C})

Carbon is in Group 14 of the periodic table. Therefore, it has 4 valence electrons.

Key concepts

Periodic Table

The periodic table is an organized chart of elements. Elements in the same column, called a group, share similar chemical properties. They are arranged in increasing atomic number from left to right. Knowing an element's position in the periodic table can help you determine its number of valence electrons. For instance, the groups 1-2 and 13-18 indicate the number of valence electrons an element possesses. Elements of the same group have the same number of valence electrons, which leads to similar chemical behaviors among the group members. By simply locating an element's group, you can infer important properties, like its reactivity and bonding behavior.

The periodic table also reflects periodic trends such as electronegativity, atomic radius, and ionization energy. These properties change predictably as you move across or down the table.

Chemical Reactivity

Chemical reactivity refers to how easily an element undergoes a chemical reaction. It largely depends on the number of valence electrons in the outer shell. For example, elements with one or two valence electrons (like those in Groups 1 and 2) tend to lose electrons easily and are very reactive metals. Conversely, elements with nearly full valence shells (like those in Groups 16 and 17) tend to gain electrons and are highly reactive non-metals.

Alkali metals (Group 1) are highly reactive and readily lose their single valence electron to form positive ions. On the other hand, halogens (Group 17) are highly reactive non-metals that gain an electron to achieve a full valence shell. The noble gases (Group 18) have full valence shells, making them least reactive. Understanding these concepts helps predict how elements will interact during chemical reactions.

Group Number

The group number in the periodic table can tell us a lot about an element, especially about its valence electrons. For groups 1-2 and 13-18, the group number corresponds to the number of valence electrons. This is a critical piece of information when trying to determine how an element will bond with others.

For example:

• Hydrogen (H), in Group 1, has 1 valence electron.
• Fluorine (F), in Group 17, has 7 valence electrons.
• Magnesium (Mg), in Group 2, has 2 valence electrons.

Elements in the same group share this valence electron characteristic, which leads to similar chemical properties and reactivity. By knowing the group number, predicting an element’s behavior in chemical reactions becomes straightforward. This is fundamental for understanding both basic and more complex chemical concepts.