Question

How many valence electrons does each of the following atoms have? a. nitrogen, \(Z=7\) b. chlorine, \(Z=17\) c. sodium, \(Z=11\) d. aluminum, \(Z=13\)

Short answer

a. Nitrogen: \(5\) valence electrons b. Chlorine: \(7\) valence electrons c. Sodium: \(1\) valence electron d. Aluminum: \(3\) valence electrons

Step-by-step solution

a. Nitrogen (Z=7)

First, let's determine the electron configuration of nitrogen with atomic number (Z) of 7. It means that nitrogen has 7 electrons surrounding its nucleus. 1s²2s²2p³ Now, let's examine nitrogen's electron configuration. We are interested in the outermost shell, which is shell 2. Counting the electrons in shell 2 gives us: 2s²2p³ = 2 + 3 = 5 valence electrons

b. Chlorine (Z=17)

Now let's find the electron configuration of chlorine (Z = 17). It has 17 electrons surrounding its nucleus. 1s²2s²2p⁶3s²3p⁵ The outermost shell is shell 3. Counting the electrons in shell 3 gives us: 3s²3p⁵ = 2 + 5 = 7 valence electrons

c. Sodium (Z=11)

Next, let's determine the electron configuration of sodium (Z = 11), with 11 electrons surrounding its nucleus. 1s²2s²2p⁶3s¹ The outermost shell is shell 3. Counting the electrons in shell 3 gives us: 3s¹ = 1 valence electron

d. Aluminum (Z=13)

Finally, let's determine the electron configuration of aluminum (Z = 13), having 13 electrons surrounding its nucleus. 1s²2s²2p⁶3s²3p¹ The outermost shell is shell 3. Counting the electrons in shell 3 gives us: 3s²3p¹ = 2 + 1 = 3 valence electrons Now we have the valence electrons for all atoms: a. Nitrogen: 5 valence electrons b. Chlorine: 7 valence electrons c. Sodium: 1 valence electron d. Aluminum: 3 valence electrons

Key concepts

Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's electron shells and subshells. It's like an address that tells you where each electron is within the atom. This configuration helps us understand the behavior of elements in chemical reactions. Electrons fill orbitals in a specific order, following the principles known as Pauli Exclusion Principle, Hund’s Rule, and the Aufbau Principle.

- **Pauli Exclusion Principle** states that no two electrons can have the same set of four quantum numbers. This means each electron in an atom has a unique "address." - **Hund's Rule** suggests that electrons will fill an empty orbital before they pair up in the same orbital. - **Aufbau Principle** advises that electrons will occupy the lowest energy level available, filling up in the order: 1s, 2s, 2p, 3s, 3p, 4s, and so on.

Knowing the electron configuration allows us to determine how many electrons are in the outermost shell, also known as valence electrons, which are important for predicting how chemical reactions will occur.

Periodic Table

The periodic table is a systematic layout of chemical elements, organized by increasing atomic number. It is divided into periods and groups, where each period represents elements with the same number of atomic orbitals, and each group contains elements with similar properties due to having the same number of valence electrons.

The periodic table's arrangement assists in predicting the chemical behavior of elements. Elements to the right, except for noble gases, generally have more valence electrons and different chemical reactivity compared to those on the left.

Groups with the same outer electron configuration display similar chemical properties, making the periodic table a valuable tool for chemists for understanding the relationships between elements and predicting their chemical interactions.

Atomic Number

The atomic number is a unique identifier for chemical elements, representing the number of protons in the nucleus of an atom and determining the element's identity. For neutral atoms, the atomic number is also equal to the number of electrons. For example, nitrogen (N), chlorine (Cl), sodium (Na), and aluminum (Al) have atomic numbers of 7, 17, 11, and 13, respectively.

This atomic number is central to understanding the arrangement of elements in the periodic table, as it increases sequentially from left to right. The atomic number not only identifies an element but also implies its electron configuration, which in turn, dictates the element's chemical properties and behaviors.

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom, each defined by its atomic number. There are over 100 known elements, each with its unique set of characteristics. They are the fundamental building blocks of matter and are categorized into metals, nonmetals, and metalloids, based on their properties.

- **Metals**: Typically shiny, good conductors of heat and electricity, and are malleable. - **Nonmetals**: Usually not shiny, poor conductors of heat and electricity, and are brittle in solid form. - **Metalloids**: Display properties intermediate between metals and nonmetals.

The study of these elements, and how they interact, forms the core of chemistry as a science. Understanding elements' electron configurations helps explain and predict their behavior in chemical reactions, such as the number of valence electrons available for bonding. This is crucial for scientists in designing materials and compounds with desired properties.