d. What are sub-atomic particles? Write down their position in an atom.
e. What is meant by the atomic mass of an atom? Write down the atomic mass of oxygen, sodium, aluminium, and argon.
f. Define atomic number and atomic weight.
g. What is 2n² rule? Calculate the maximum number of electrons found in shell N by using this rule.
h. What is valency? Write down the valency of oxygen, magnesium, and calcium.
i. What are valence electrons? Write with an example.
j. What is duplet and octet state? Describe with an example of each.
k. What is molecular formula? Write down the method of writing molecular formula.
l. What is molecular weight? How does it differ from atomic weight?
Answer (2)
Sub-atomic particles include protons, neutrons, and electrons, with protons and neutrons in the nucleus and electrons in the electron cloud. The atomic mass is the weighted average mass of isotopes, and valency is the ability to bond based on outer electrons. The 2n² rule determines electron capacity in shells, where the maximum for shell N is 32; valence electrons determine bonding behavior, and molecular formulas depict the number and type of atoms in a compound.
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d. Sub-atomic particles are the smaller constituents of an atom, mainly protons, neutrons, and electrons.
Protons are positively charged particles found in the nucleus of an atom.
Neutrons are neutral particles, also found in the nucleus.
Electrons are negatively charged particles orbiting the nucleus in electron shells.
e. The atomic mass of an atom is the weighted average mass of an atom's naturally occurring isotopes, measured in atomic mass units (amu).
Oxygen : 16 amu
Sodium : 23 amu
Aluminium : 27 amu
Argon : 40 amu
f. The atomic number is the number of protons in the nucleus of an atom, which defines the element.
The atomic weight, also known as relative atomic mass, is the average mass of atoms of an element, calculated using the abundance of isotopes.
g. The 2n² rule is a formula to determine the maximum number of electrons that can be accommodated in an electron shell, where 'n' is the shell number.
For shell N (n=4), the maximum number of electrons = 2(4)² = 32
h. Valency is the combining capacity of an element, determined by the number of electrons an atom can lose, gain, or share.
Oxygen : Valency of 2
Magnesium : Valency of 2
Calcium : Valency of 2
i. Valence electrons are the electrons in the outermost shell of an atom. They determine the chemical properties and reactivity of the element.
Example: Oxygen has 6 valence electrons as its electron configuration is 1s² 2s² 2p⁴.
j. Duplet state : Atoms with 2 electrons in their outermost orbit achieve stability, similar to helium.
Example: Helium (He), with an electron configuration of 1s².
Octet state : Atoms with 8 electrons in their outermost orbit achieve stability, similar to noble gases.
Example: Neon (Ne), with an electron configuration of 1s² 2s² 2p⁶.
k. The molecular formula represents the number and types of atoms in a molecule. It's written by combining the chemical symbols of elements and their respective quantities.
Example: For water (H₂O), there are 2 hydrogen atoms and 1 oxygen atom.
l. The molecular weight is the sum of the atomic weights of all atoms in a molecule. It differs from atomic weight as it represents entire molecule masses, rather than individual atoms.
Example: The molecular weight of water (H₂O) is approximately 18 amu (2*1 for H + 16 for O).
