Explanation

The universal gas constant R appears in the ideal gas law PV = nRT and has a value of 8.314 joules per mole per kelvin (J/mol·K) in SI units.  

Other values:  

- 0.0821 L·atm/mol·K is R in L·atm units  

- 1.987 cal/mol·K is R in calories  

- 9.8 m/s² is the acceleration due to gravity, not related to R

Explanation

The speed of light in a vacuum is approximately 3 × 10⁸ meters per second (m/s).  

This is a fundamental constant in physics, denoted by c, and is used in equations such as E = mc² and c = λ × f, where λ is wavelength and f is frequency.

Explanation

The formula for wave speed is wave speed = wavelength * frequency, so the product of wavelength and frequency represents the speed of a wave. 

Explanation

The period number represents the number of electron shells (energy levels) an element has.

For example, elements in period 2 have electrons in 2 shells.

Explanation

Across a period, the atomic number increases, meaning more protons in the nucleus.

- This results in a stronger attraction between the nucleus and the electrons.

- Since the electrons are added to the same energy level without much shielding, more energy is needed to remove an electron.

Explanation

Alkali metals are in Group 1 of the periodic table.

These elements are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). 

Explanation

Halogen elements are found in Group 17 (also known as Group VIIa or Group 7A) of the periodic table.

This group includes the elements fluorine, chlorine, bromine, iodine, and astatine, as well as the recently discovered tennessine. 

Explanation

Noble gases are also known as inert gases, rare gases, or aerogens.

They are members of Group 18 on the periodic table

And are known for their low reactivity due to their full valence electron shells,

Which makes them very stable and unreactive with other elements. 

Explanation

Transition elements are found in the center of the periodic table and belong to the d-block, where the d-orbitals are being filled.

These elements typically have variable oxidation states and form colored compounds.

Explanation

An ionic bond is formed through the transfer of one or more electrons from one atom to another,

This results in the formation of oppositely charged ions (cations and anions) that are attracted to each other.

This transfer leads to a stable electron configuration for both atoms involved.