Atomic Structure and Subatomic Particles

Atomic Structure and the Periodic Table

• All substances consist of atoms.
• Atoms are extremely small.
• Atoms typically have a radius of about 0.1 nm (1x10^-10 m).
• Atoms consist of three subatomic particles: protons (p), electrons (e), and neutrons (n).

Subatomic Particles

• Protons have a relative charge of +1 and a relative mass of 1.
• Neutrons have a relative charge of 0 and a relative mass of 1.
• Electrons have a relative charge of -1 and a relative mass of approximately 1/2000.

The Nucleus

• The nucleus is located in the middle of the atom.
• It contains protons and neutrons.
• The nucleus has a radius of around 1x10^-14 m.
• The nucleus has a positive charge due to the presence of protons.
• Most of the atom's mass is concentrated in the nucleus.

Electrons

• Electrons move around the nucleus in electron shells.
• They are negatively charged, tiny, and cover a lot of space.
• The volume of electron orbits determines the size of the atom.
• Electrons have virtually no mass.

Atomic Number and Mass Number

• The atomic number indicates the number of protons in the atom.
• Mass number equals the number of protons plus the number of neutrons.
• To find the number of neutrons, subtract the atomic number from the mass number.
• Atoms are neutral overall because they have the same number of protons and electrons.
• The charge on electrons is the same size as the charge on protons, but opposite, so the charges cancel out.

Ions

• In ions, the number of protons does not equal the number of electrons.
• Ions are charged particles that have either lost or gained electrons.
• Positive ions lose electrons.
• Negative ions gain electrons.

Elements

• An element is a substance made of atoms with the same number of protons in their nucleus.
• There are about 100 different elements.
• All atoms of a particular element contain the same number of protons. Additionally, different elements contain atoms with different numbers of protons.
• Atoms can be represented by symbols such as C, O, Mg, Na, Fe, and Pb.

Isotopes

• Isotopes are different forms of the same element, containing the same number of protons but a different number of neutrons.
• Isotopes have the same atomic number, but different mass numbers.
• Relative atomic mass (Ar) is utilized instead of mass number when referring to "the element on a whole" as different isotopes exist for elements.
• Relative atomic mass accounts for the different atomic masses and abundances of each isotope that constitutes the element.

Relative Atomic Mass Formula

• Relative atomic mass (Ar) is calculated as the sum of (isotope abundance x isotope mass number) divided by the sum of abundances of all isotopes.

Compounds

• When elements react, atoms combine with other atoms to form compounds.
• Compounds are substances formed from two or more elements with atoms in fixed proportions, held together by chemical bonds.
• Forming bonds involves atoms giving away, taking, or sharing electrons; only electrons are involved.
• Separating the original elements of a compound is usually difficult.
• A compound made from a metal and a non-metal consists of ions.
• Metal atoms lose electrons to form positive ions, while non-metal atoms gain electrons to form negative ions.
• Opposite charges of ions strongly attract each other, creating ionic bonding.
• Sodium chloride, magnesium oxide, and calcium oxide are examples of ionic compounds.
• A compound formed from non-metals consists of molecules, where each atom shares an electron with another atom, creating covalent bonding.
• Hydrogen chloride gas, carbon dioxide, and water are examples of covalent compounds.

Properties of Compounds

• The properties of a compound are usually totally different from the properties of the original elements.

Chemical Equations

• Chemical equations can be written as word equations and symbol equations
• Methane + Oxygen → Carbon Dioxide + Water (CH4 + 02 → CO2 + H2O)
• Magnesium + Oxygen → Magnesium Oxide (Mg + 02 → MgO)
• H2SO4 + NaOH → Na2SO4 + H2O
• Fe + Cl2 → FeCl3

Mixtures and Chromatography

• In a compound, there is unlike a chemical bond between the different parts of a mixture.
• The parts of the mixture can be other elements or compounds and they can be separated out by physical methods such as filteration, crystallisation and chromato-graphy.
• Air is a mixture of gases (mainly N2, O2, CO2 and Ar), which can be separated out fairly easily.
• Crude oil is a mixture of different length hydrocarbon molecules.
• Properties of a mixture are like the properties of the seporate parts.

Paper Chromatography

• End result pattern of spots is called a chromatogram.

More Separation Techniques

• Includes Filteration and crystallisation

Filteration

• This method is used to separate insoluble solids from liquids
• It can be used in purification, as well as in impurities in a reaction mixture can be separated out using filteration.

Crystallisation

• There are two ways to separate a soluble salt from a solution:
  • Evaporation
  • Crystallisation

Evaporation

• Pour the solution into an evaporating dish.
• Slowly heat the solution.
• Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated.
• Eventually, crystals will start to form.
• Keep heating Keep heating the evaporating dish unhi all you have left and dry crustals.
• The salt doesn't not decompose use if not It's heated.
• Otherwise, use crystallisation.

Crystallisation

• Pour the solution into an evaporating dish and gently neat the solution.
• The solvent will get more concentrared you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave the solution to 1001.
• The salt should start form corystals, concentrate the solution.
• Filter the crystals out of the solution and leave them in warm place to dry/ oven a desiccator.

Separating Rock Salt

• Components include a mixture of salt and sand.
• Salt and sand are both compounds.
• Salt dissolves in water but not sand.
• Grind salt and sand mix together.
• Dissolve in water to disolve salt.
• Filter the mixture to collect grains of sand.
• The salt passes through the filter
• Evaporate the moisture until the salt so that it forms dry crystals.

Learn about the fundamental components of atoms, including protons, neutrons, and electrons. Explore the structure of the nucleus and the arrangement of electrons in shells. Understand the charges and relative masses of subatomic particles and their role in determining atomic properties.