Atoms, Molecules, and Chemical Formulae

• The lesson examines the particles found in atoms and molecules.
• Keywords are atoms, molecules, elements, and compounds.
• Starter questions include naming the four main atmospheric gases and knowing their chemical formulae.
• Learning Objectives (AO) include:
• Recognizing the difference between atoms and molecules
• Comparing compounds and molecules
• Using models to represent elements, mixtures, and compounds

Air Composition

• Air is a mixture of gases that makes up Earth's atmosphere.
• Air consists of approximately 78% nitrogen, 21% oxygen, variable amount of water vapor, 0.9% argon, 0.04% carbon dioxide, and trace gases.

Chemical Formulae

• A chemical formula indicates the number of atoms of elements in a molecule, using element symbols.
• For example, carbon dioxide (CO₂) has two oxygen atoms bonded to one carbon atom.

Atoms

• Atoms are the simplest form of matter.
• Atoms can be represented by single circles or spheres.
• Examples of atoms include Helium (He), Argon (Ar), Neon (Ne), and Radon (Rn).

Molecules

• Molecules consist of two or more atoms bonded together, and atoms can be the same element bonded together.
• Most substances are molecules.
• Examples of molecules include hydrogen (H₂), chlorine (Cl₂), carbon dioxide (CO₂), water (H₂O), and methane (CH₄).

Elements vs. Compounds

• Elements contain only one type of atom and cannot be split into simpler substances, like oxygen (O₂).
• Compounds contain different types of atoms bonded together.
• All compounds are molecules, for example carbon dioxide (CO₂).

Elements

• Elements are pure substances consisting of one type of atom.
• Elements can be found on the periodic table.
• Examples are Diamond (C) & Copper (Cu)

Compounds

• Compounds are different types of atoms bonded together
• Example is Hydrochloric acid (HCl)

Identifying Elements and Compounds

• When looking at diagrams, determine if the image is Oxygen (O₂) or Water (H₂O)
• An oxygen diagram shows (O₂) whereas, a water diagram shows (H₂O)
• Elements contain only one kind of atom.
• Compounds contain two or more kinds of atoms.

Air as a Mixture

• Air isn't an element, or compound, but a mixture containing elements like nitrogen, argon, and oxygen, plus compounds like carbon dioxide and water.
• Argon is an atom, not a molecule.
• Carbon dioxide is a compound, as opposed to elements.
• Oxygen and nitrogen are molecules

Tasks

• Task1 : Discussion about what air is, is it an element, compound or something else, air is a mixture
• Task 2 : Explain with linking about statements about air: is argon the odd one out, it is an atom, not a molecule; is air a pure substance, which it is not; and is oxygen and nitrogen compounds? No, they are molecules.
• Task 3 : Build a molecule simulation https://phet.colorado.edu/en/simulations/build-a-molecule

Developing, Securing and Excelling

• Developing includes drawing the diagrams
• Securing includes listing names of the elements in each molecule, writing their symbols and stating how many there are
• Excelling includes stating the chemical formula for each molecule and stating whether the picture is showing an element or a compound and why
• Table showing how molecules are arranged in a variety of different layouts.
• Label each chemical as an atom or molecule, then label each one as an element or a compound
• Neon (Ne), Oxygen (02), Water (H₂O), Hydrogen (H₂), Glucose (C6H12O6), Methane (CH4), Ethyne (C2H2) and Carbon dioxide (CO₂) are examples to label
• Count the atoms for each chemical.

Understanding gases

• Oxygen is found as oxygen molecules that contain two oxygen atoms
• Carbon dioxide is also found as molecules, the molecules contain two oxygen atoms that separated by one carbon atom
• Nitrogen is also found as molecules, in a similar way to oxygen
• Argon is found as signal atoms of the element