Atoms and Elements

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What is an atom?

An atom is the smallest unit of matter that retains the identity of the substance. It consists of protons, neutrons, and electrons.

What is the atomic number?

The atomic number, represented by 'Z', is the number of protons in the nucleus of an atom.

What are the subatomic particles in an atom?

Protons, neutrons, and electrons.

How do you calculate the number of neutrons in an atom?

Subtract the atomic number from the atomic mass: Neutrons = Atomic Mass - Atomic Number.

What is the octet rule?

The octet rule states that atoms are most stable when they have eight electrons in their valence shell.

What is valency?

Valency is the number of atoms an element can gain, lose, or share to be stable.

What is the symbol for the atomic number?

Z

What is the mass number or nucleon number?

It's the total number of protons and neutrons in an atom's nucleus.

How is valency determined for an element like carbon?

Carbon has 4 electrons in the second shell and can gain or lose 4 electrons to be stable.

What is a pure element?

It is made of only one type of atom and cannot be broken down into simpler substances.

Give an example of a compound.

Water (H2O) or salt (NaCl).

What are the differences between mixtures and compounds?

Mixtures are physically combined and have varying ratios, while compounds are chemically bonded and have fixed ratios.

What is a homogeneous mixture?

A mixture with uniform composition throughout, like a solution.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

How are elements organized in the periodic table?

By increasing atomic number, and they are grouped by similar properties.