Question

State the number of valence electrons for each of the following elements: (a) \(\mathrm{H}\) (b) B (c) \(N\) (d) F (e) \(\mathrm{Ca}\) (f) Si (g) O (h) Ar

Short answer

(a) 1, (b) 3, (c) 5, (d) 7, (e) 2, (f) 4, (g) 6, (h) 8 valence electrons.

Step-by-step solution

Determine Group for Each Element

The number of valence electrons of an element depends on its position in the periodic table, particularly the group number. Elements in the same group have the same number of valence electrons.

Identify Group and Determine Valence Electrons

- (a) **Hydrogen () is in Group 1**, so it has 1 valence electron. - (b) **Boron (B) is in Group 13**, meaning it has 3 valence electrons. - (c) **Nitrogen (4) is in Group 15**, so it has 5 valence electrons. - (d) **Fluorine (F) is in Group 17**, therefore, it has 7 valence electrons. - (e) **Calcium (60) is in Group 2**, which means it has 2 valence electrons. - (f) **Silicon (Si) is in Group 14**, indicating it has 4 valence electrons. - (g) **Oxygen (3) is in Group 16**, thus it has 6 valence electrons. - (h) **Argon (Ar) is in Group 18**, which gives it 8 valence electrons (except Helium, which has 2).

Key concepts

Periodic Table

The periodic table is a powerful tool in understanding chemical elements. It arranges elements in order of increasing atomic number, which is the number of protons in an atom's nucleus. This arrangement also demonstrates periodic patterns in the physical and chemical properties of the elements.

Elements are placed in rows known as periods and columns called groups or families. The periodic table helps us predict how elements will behave in chemical reactions, because elements in the same group often have similar properties. It's also essential for determining the number of valence electrons, which are the electrons involved in bonding.

For example, elements within the same group have the same number of valence electrons, which directly influences their chemical properties and reactivity. By looking at an element's position on the periodic table, you can quickly identify its valence electrons, thus predicting its potential chemical interactions.

Element Groups

Element groups are columns of the periodic table, indicating elements that share common properties. There are 18 recognized groups, and each has its own characteristic features. The most significant aspect of these groups is that all elements within a group have the same number of valence electrons.

Here’s a quick overview of some key groups:

• Group 1 - Alkali Metals, such as lithium and sodium.
• Group 2 - Alkaline Earth Metals, like magnesium and calcium.
• Group 17 - Halogens, including fluorine and chlorine.
• Group 18 - Noble Gases, which are mostly inert, like argon and neon.

Each group's elements tend to react similarly because they have the same number of valence electrons. For example, halogens in Group 17 always have seven valence electrons, making them highly reactive such that they eagerly gain one electron to achieve a stable configuration.

Chemical Elements

Chemical elements are fundamental substances that can't be broken down into simpler substances through chemical means. Each element is defined by its atomic number, which is the number of protons in its nucleus.

Elements are the building blocks of matter, and more than 100 elements are organized in the periodic table. They vary widely in their properties and uses, ranging from metals like gold and silver to gases such as hydrogen and oxygen.

Each chemical element has unique physical and chemical properties, which are influenced by its electron configuration. For instance, oxygen is essential for respiration due to its ability to form strong double covalent bonds, while metals like iron are key structural materials that are durable due to their specific atomic arrangements and bonding.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's electron shells. This is crucial for understanding an element's chemical behavior. Electrons are arranged in energy levels or shells around the nucleus, with each shell holding a certain maximum number of electrons.

The configuration is typically expressed using the notation that includes numbers, letters, and superscripts, such as \(1s^2 2s^2 2p^6\) for a full second shell. Electrons fill the lowest energy levels first before moving to higher ones, following the Aufbau principle.

Understanding electron configuration enables us to predict an element's properties. For example, elements in the same column on the periodic table have similar valence electron configurations, which accounts for their similar chemical properties. Also, knowing an element’s electron configuration is key to determining its placement on the periodic table, as it directly relates to the number of valence electrons that control bonding.