Problem 90 - Chemistry Matter and Change

Question

Draw an electron-dot structure for an atom of each element. $$\begin{array}{l}{\text { a. carbon }} \\ {\text { b. arsenic }} \\ {\text { c. polonium }} \\ {\text { d. potassium }} \\ {\text { e. barium }}\end{array}$$

Step-by-Step Solution

Answer

Carbon: 4 dots, Arsenic: 5 dots, Polonium: 6 dots, Potassium: 1 dot, Barium: 2 dots.

Step 1: Understand Valence Electrons

The number of valence electrons for an element determines its electron-dot structure. Valence electrons are the electrons in the outermost shell of an atom.

Step 2: Determine Valence Electrons for Each Element

- **Carbon (C)**: Atomic number 6, with electron configuration of 1s² 2s² 2p². It has 4 valence electrons in the 2p and 2s orbitals. - **Arsenic (As)**: Atomic number 33, with electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³. It has 5 valence electrons in the 4p and 4s orbitals. - **Polonium (Po)**: Atomic number 84, with electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁴. It has 6 valence electrons in the 6p and 6s orbitals. - **Potassium (K)**: Atomic number 19, with electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. It has 1 valence electron in the 4s orbital. - **Barium (Ba)**: Atomic number 56, with electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s². It has 2 valence electrons in the 6s orbital.

Step 3: Draw the Electron-Dot Structure

- **Carbon (C)**: Place 4 dots around the symbol 'C', one on each side, to represent 4 valence electrons. - **Arsenic (As)**: Place 5 dots around the symbol 'As'. Keep in mind to pair up only three electrons. - **Polonium (Po)**: Place 6 dots around the symbol 'Po'. Ensure two pairs and two single dots. - **Potassium (K)**: Place 1 dot next to the symbol 'K'. - **Barium (Ba)**: Place 2 dots next to the symbol 'Ba'.

Key Concepts

Valence Electrons

Valence electrons are crucial in understanding how elements interact and form bonds. They are the outermost electrons present in an atom's electron shells. The primary role of valence electrons is to determine the reactivity of an element since they are the electrons involved in chemical bonding.

Why are they important? Because they can be lost, gained, or shared during chemical reactions, helping form compounds. The number of valence electrons can vary:

• Elements with the same number of valence electrons exhibit similar chemical properties.
• They determine the element's ability to bond with others.

For example, carbon has four valence electrons, enabling it to form four bonds with other elements.

Atomic Structure

The atomic structure of an element gives a detailed look into what an atom consists of. Every atom is made up of protons, neutrons, and electrons.

Here's a brief breakdown:

• Protons and neutrons reside in the atom's nucleus, at its center.
• Electrons orbit around the nucleus in specific regions known as electron shells or energy levels.

Understanding the atomic structure helps in predicting how an element will behave. The composition of the nucleus (protons and neutrons) determines the atomic number and, consequently, the identity of the chemical element. Meanwhile, the distribution of electrons across various shells dictates the electronic configuration of the atom.

Electron Configuration

Electron configuration provides insight into the arrangement of electrons in an atom. This configuration is essential for understanding many properties of an element, including its chemical behavior and bonding characteristics.

How is electron configuration written?

• It uses numbers and letters to indicate the energy levels and sublevels where the electrons are situated.
• For instance, the electron configuration of carbon is \(1s^2 2s^2 2p^2\), showing two electrons in 1s, two in 2s, and two in 2p.

Different elements have unique electron configurations, which lead to unique properties. It determines how electrons fill the atom's shells, following principles like the Aufbau principle and Hund's rule.

Chemical Elements

Chemical elements are pure substances consisting entirely of one type of atom. These are the building blocks of everything around us and every matter is made up of a combination of different elements.

What should you know about chemical elements?

• There are over 100 known elements, each defined by the number of protons in its nucleus, also known as the atomic number.
• Elements are organized in the periodic table, which is structured to highlight recurring trends in properties known as periodicity.
• Each element has unique characteristics and can form various types of bonds with other elements.

For example, hydrogen is the lightest element with one proton, while elements like uranium have a large number of protons and neutrons. Understanding chemical elements helps us manipulate them into compounds and materials used in everyday life.