Which of the following forms of oxygen can exist freely in nature? A O, B O2, C O3

The form of oxygen that cannot exist freely in nature is atomic oxygen.

• A. O

Ions are not fundamental particles of an atom; they are atoms that have gained or lost electrons.

• B. Ions

Crystalline compounds have a regular, ordered structure, which results in a specific temperature at which all bonds break simultaneously.

• True

The regular arrangement of atoms in a crystal is known as a crystal lattice.

• C. Lattice

Step 1: Identify the given values and the formula for Hooke's Law. Given force $F = 20\, \text{N}$ and extension $x = 2\, \text{m}$. Hooke's Law states $F = kx$, where $k$ is the spring constant.

An atom consists of a central, dense nucleus containing positively charged protons and neutral neutrons. Negatively charged electrons orbit the nucleus in specific energy levels or shells. The number of protons determines the element.

• Cohesion is the attractive force between molecules of the same substance. For example, water molecules are cohesive, causing surface tension.

• Adhesion is the attractive force between molecules of different substances. For example, water adheres to glass, causing it to climb up a narrow tube (capillary action).

Young's Modulus (or modulus of elasticity) is a measure of the stiffness of an elastic material. It is defined as the ratio of tensile stress to tensile strain within the elastic limit of the material.

where $F$ is the applied force, $A$ is the cross-sectional area, $\Delta L$ is the extension, and $L_0$ is the original length.

Step 1: Calculate the spring constant ($k$) using the initial force and extension. Given initial force $F_1 = 5\, \text{N}$ and initial extension $x_1 = 0.1\, \text{m}$. Using Hooke's Law, $F_1 = kx_1$: