Atomic Structure and Chemical Reactions

Atomic Structure

• All substances are made of atoms. Atoms are the smallest part of an element.
• Elements are represented by chemical symbols (e.g., O for oxygen, Na for sodium). About 100 different elements exist.
• Compounds are formed from elements through chemical reactions. These reactions involve the formation of new substances and often energy changes.
• Compounds are made of two or more elements combined in fixed proportions. They can be represented by formulas.
• Compounds can only be broken down into their constituent elements through chemical reactions.
• Chemical reactions can be shown using word equations or symbol equations.
• Students need to know the first 20 elements in the periodic table, plus groups 1 and 7.
• Students should be able to name compounds from formulas or equations.
• Students should be able to write word equations.
• Students should be able to write balanced chemical equations.
• (Higher Tier only): students should be able to write balanced half-reactions and ionic equations.
• Mixtures are made from two or more elements or compounds not chemically bonded. The chemical properties of the components are unchanged.
• Mixtures can be separated by physical processes like filtration, crystallization, distillation, fractional distillation, and chromatography. These processes do not involve chemical reactions.
• Students should be able to describe, explain, and give examples of separation methods.
• Students should be able to suggest suitable separation methods for mixtures.

Atomic Models

• Before the electron was discovered, atoms were thought of as indivisible spheres.
• The plum pudding model proposed that an atom is a ball of positive charge with negatively charged electrons embedded within it.
• Alpha particle scattering experiments showed that the mass of an atom is concentrated in a small, positively charged nucleus. This led to the nuclear model.
• Niels Bohr proposed a model where electrons orbit the nucleus at specific distances.
• Later experiments showed that the positive charge of the nucleus can be subdivided into smaller particles called protons .
• James Chadwick's work provided evidence of neutrons in the nucleus.
• Students should be able to describe the differences between the plum pudding and nuclear models.
• Students should be able to explain why the nuclear model replaced the plum pudding model.

Subatomic Particles

• Atoms have three main subatomic particles: protons (+1 charge), neutrons (0 charge), and electrons (-1 charge).
• Protons and neutrons are found in the nucleus.
• Electrons orbit the nucleus.
• Atoms have an equal number of protons and electrons, making them electrically neutral.
• The number of protons in an atom defines its atomic number, and defines the element.
• All atoms of a given element have the same number of protons
• Atoms of different elements have a different number of protons
• Atoms are very small (radius ~0.1 nm).
• The nucleus is much smaller compared to the atom (radius ~ 10^-14 m).
• Almost all the mass is concentrated in the nucleus.

This quiz covers the fundamentals of atomic structure, including the properties of atoms and elements. Students will explore the formation and naming of compounds, as well as the representation of chemical reactions through word and symbol equations. Ideal for students preparing for examinations in chemistry.