Chemistry :Topic 1.1 :A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

1.1. A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

What are atoms?

Atoms are the smallest part of an element that can exist and make up all substances.

What do chemical symbols represent?

Chemical symbols represent an atom of an element, for example, 'Na' represents an atom of sodium.

How are compounds formed?

Compounds are formed from elements through chemical reactions, which often involve the formation of one or more new substances and energy changes.

What do compounds contain?

Compounds contain two or more elements that are chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they are formed (e.g., HCl represents 1 atom of hydrogen and 1 atom of chlorine per molecule).

How can compounds be separated into elements?

Compounds can only be separated into their constituent elements through chemical reactions.

What is a mixture?

A mixture consists of two or more elements or compounds not chemically combined together, with the chemical properties of each substance remaining unchanged.

How can mixtures be separated?

Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation, and chromatography. These processes do not involve chemical reactions and do not create new substances.

What was the first model of the atom?

Initially, atoms were thought to be tiny spheres that could not be divided.

What is the Plum Pudding Model?

The Plum Pudding Model suggests that the atom is a ball of positive charge with negative electrons embedded in it, developed after the discovery of the electron.

What did the alpha particle scattering experiment conclude?

The experiment concluded that the mass of an atom is concentrated at its center (the nucleus), which is positively charged.

What was observed during the alpha particle scattering experiment?

In the experiment, a beam of alpha particles aimed at thin gold foil was detected; some particles emerged at different angles while others bounced back, indicating the presence of a positively charged nucleus.

What concept did Neil Bohr introduce?

Neil Bohr suggested that electrons orbit the nucleus at specific distances, a theory supported by experimental data.

What did later experiments reveal about nuclear charge?

The positive charge of a nucleus is made up of smaller particles called protons, each with the same charge.

What did James Chadwick discover?

He provided evidence for the existence of neutrons in the nucleus.

What is the atomic number?

The number of protons in an atom

What are the relative charges of subatomic particles?

• Proton: +1

• Neutron: 0

• Electron: -1

Why is an atom neutral overall?

Because the number of protons equals the number of electrons.

What is the approximate size of an atom?

About 0.1 nm in radius.

How does the size of the nucleus compare to the atom?

The nucleus is less than 1/10,000 the size of the atom.

Where is most of the atom’s mass found?

In the nucleus.

What are the relative masses of subatomic particles?

• Proton: 1

• Neutron: 1

• Electron: Very small

What is mass number?

The total number of protons and neutrons in an atom.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What is relative atomic mass?

The weighted average mass of an element, considering isotope abundance.

How do you calculate relative atomic mass?

(mass × abundance)+(mass × abundance) / 100

Where do electrons occupy in an atom?

The lowest available energy levels (shells closest to the nucleus).

What does electronic structure show?

The number of electrons in each shell.