Chemistry: Atoms, Molecules, and Compounds PDF

Recall that all matter is composed of atoms and has mass - The particles which make up atoms are called protons, Neutrons and electrons. - protons and neutrons are found in the nucleus of the atom. - Particles called electrons orbit around the nucleus. They have a negative...

Recall that all matter is composed of atoms and has mass - The particles which make up atoms are called protons, Neutrons and electrons. - protons and neutrons are found in the nucleus of the atom. - Particles called electrons orbit around the nucleus. They have a negative charge. - The smallest particle in the atom is the electron. It is about 1840 times smaller than the proton and neutron. - Atoms are normally stable because they have the same number of protons and electrons. - Atoms with the same number of protons but different numbers of neutrons are called isotopes Different types of particles: atoms and molecules atoms: are the smallest particles into which matter can be broken down Molecules: contain two or more atoms held together by chemical bonds Different types of substances: mixtures and pure substances mixtures: are impure substances – they have two or more different types of particles, which can be separated using physical separation techniques (e.g. filtration etc.) as they are not chemically bonded together pure substances contain only one type of particle – as their particles are all identical, they can’t be separated into simpler substances using physical techniques. Different types of pure substances: elements and compounds an element is the simplest type of substance, containing one type of atom only a compound contains two or more types of atom, as it is made up of two or more elements chemically bonded together – to separate it into its component elements, chemical processes must be used to break these bonds. Particles of elements and compounds: an element’s particles can be either single atoms, or molecules containing identical atoms (e.g. oxygen molecules, O2) compounds are never made up of single atoms – their molecules contain atoms of the component elements bonded together in the same proportion, shown by its formula (e.g. water molecules contain 2 hydrogen atoms bonded to 1 oxygen atom, shown by the formula H2O). Number of neutrons = Mass number - protons  Elements gain or lose electrons to attain a full outer shell. Therefore atoms which do not have a full outer shell will react with other atoms to become stable. In these chemical reactions atoms will give up or accept electrons to/from other atoms to obtain a complete outer shell like the Noble gases in group 8. The result is a stable compound. When an atom gains or loses electrons it becomes a charged atom called an ion. Many atoms form ions when they take part in chemical reactions. The charge on the atom is called valency. Ionic compounds form when metallic elements bond with non-metallic elements. Metal atoms tend to lose electrons to form positive ions when they react with non-metals to form compounds. Non-metal atoms tend to gain electrons to form negative ions when they react with metals to form compounds. Identify a range of compounds using their common names and chemical formulae Ionic compounds are normally a combination of a metal, along with one or more non metals. The names given to the ionic compounds start with the metal. The rest of the name depends on the non-metals present. The ionic compound formed when iron reacts with oxygen is called iron oxide. This type of compound is known as an oxide. In a similar way, ionic compounds that contain a metal and the single non-metal fluorine are known as fluorides. Therefore, a compound made by the reaction between iron and fluorine would be called iron fluoride. Table 1 shows the types of compounds formed by some other non-metals. Remember – these names are used only if one single non-metal is present. Single Type of non-metal compound Oxygen Oxide Fluorine Fluoride Sulfur Sulfide Chlorine Chloride Bromine Bromide Iodine Iodide  Hydrogen Hydride Other ionic compounds have more than one non-metal. For example, the element lead might react with both sulfur and oxygen to form the compound lead sulfate. The fact that this compound ends with ‘ate’ tells us that it must contain oxygen. Examples of compounds containing oxygen and one other non-metal are shown in table 2. Non-metals Type of included compound Sulfur and Oxygen Sulfate Carbon and Oxygen Carbonate Nitrogen and Nitrate Oxygen Chlorine and Oxygen Chlorate The last types of ionic compounds we are going to consider include a metal, and a group of nonmetals. If the group contains just hydrogen and oxygen then a hydroxide is formed (not a hydrate, as you might expect). If the group contains hydrogen, carbon and oxygen then a hydrogen carbonate is formed. Classify compounds into groups based on common chemical characteristics - including acids, bases and salts Acids are substances that can donate a proton (H⁺ ion) or accept an electron pair Bases are substances that can accept protons (H⁺ ions) or donate an electron pair, often producing OH⁻ ions in solution. Salts are ionic compounds formed by the neutralization reaction between an acid and a base. Blue litmus turns red in acid Red litmus turns blue in base pH paper changes colour in acids and bases and must be compared to a colour chart to read pH Universal indicator changes colour in acids and bases and must be compared to a Universal indicator colour chart to read pH Alkali: a base that dissolves in water alkaline solution: a solution that contains a base An indicator is a substance that changes colour in the presence of an acid or a base. pH: a measure of how alkali or acidic a solution is Neutral pH: 7 Acid: any substance that forms an aqueous solution with a pH less than 7 Base: any substance with a pH greater than 7 Alkalis are a subgroup of a Base - A base that desloves in water to form a solution greater than 7 - A chemical test for an acid is to add metal carbonate to it, the evolution of bubbles of carbon dioxide is evidence that an acid was used Investigate a range of types of important chemical reactions that occur in non-living systems including: ○ the reaction of acids with metals Acid + metal → salt + hydrogen - To test for hydrogen we do a “pop test”, which is when a burning splint held near to the top of the test tube. The positive result is a squeaky pop sound as the hydrogen reacts with oxygen in the air in a small explosion. Example: - Hydrochloric acid + potassium hydroxide → potassium chloride + water ○ the reaction of acids with carbonates Carbonate + acid = water + salt + carbon dioxide To confirm carbon dioxide has been formed, the gass from the substance is passed through lime water (a solution of calcium hydroxide and water) - After a few seconds, the water should become a white, milky colour ○ neutralisation Acid + base → salt + water Example: Hydrochloric acid + sodium hydroxide → sodium chloride + water - The strength of both the acid and the base are lowered - They are brought to a neutral point Construct word equations from observations and written descriptions of a range of chemical reactions - Metal and Acid Reactions When a metal reacts with an acid, it typically produces a salt and hydrogen gas. - Observation: Bubbles form as zinc metal is added to hydrochloric acid. - Word Equation: Zinc + Hydrochloric acid → Zinc chloride + Hydrogen gas - Acid and Carbonate Reactions An acid reacting with a carbonate produces a salt, water, and carbon dioxide gas. - Observation: Effervescence (fizzing) occurs as calcium carbonate is added to hydrochloric acid. - Word Equation: Calcium carbonate + Hydrochloric acid → Calcium chloride + Water + Carbon dioxide - Acid and Base An acid reacting with a base produces a salt and water. - Observation: When sodium hydroxide is added to hydrochloric acid, the solution becomes neutral. - Word Equation: Sodium hydroxide + Hydrochloric acid → Sodium chloride + Water QUESTIONS Name the compounds formed when these pairs of elements react together (no other elements are involved in the reaction). a. iron and chlorine → b. lead and oxygen → c. calcium and fluorine → d. bromine and aluminium → e. sulfur and potassium → f. copper and oxygen → g. hydrogen and sodium → h. magnesium and bromine → i. fluorine and silver → j. nickel and chlorine → Name the compounds formed when these elements react together. a. copper, sulfur and oxygen → ______________________________ b. lead, oxygen and nitrogen → ______________________________ c. oxygen, potassium and carbon → ______________________________ d. zinc, nitrogen and oxygen → ______________________________ e. oxygen, aluminium and sulfur → ______________________________ Name the compounds formed when these elements bond together. 1. calcium, hydrogen and oxygen → __________________ 2. sodium hydrogen, carbon and oxygen → __________________ 3. potassium, hydrogen, carbon and oxygen → __________________ 4. potassium, hydrogen and oxygen → __________________ Name the compounds formed by these sets of elements a. lead and chlorine → __________________________________ b. iron, nitrogen and oxygen → __________________________________ c. lithium and fluorine → __________________________________ d. sodium, hydrogen and oxygen → __________________________________ e. sulfur, potassium and oxygen → __________________________________ f. zinc and oxygen → __________________________________ g. hydrogen, sodium, carbon and oxygen → __________________________________ h. lead and bromine → __________________________________ i. carbon, silver and oxygen → __________________________________ j. iron and sulfur → __________________________________ k. oxygen, hydrogen and lithium → __________________________________ l. silver and iodine → __________________________________ m. magnesium, nitrogen and oxygen → __________________________________ n. calcium and fluorine → __________________________________ o. calcium, hydrogen, carbon and oxygen → __________________________________ Sodium carbonate +Hydrochloric acid → Potassium carbonate + Hydrochloric acid → Magnesium carbonate + Hydrochloric acid → Nitric acid + copper carbonate → 1. Hydrochloric acid + barium carbonate → 2. Hydrochloric acid + magnesium carbonate → 3. Hydrochloric acid + potassium carbonate → 4. Nitric acid + beryllium carbonate → 5. Nitric acid + lithium carbonate → 6. Nitric acid + calcium carbonate → 7. Sulfuric acid + copper carbonate → 8. Sulfuric acid + zinc carbonate → 9. Sulfuric acid + iron carbonate →