Chemistry

• The electrons are located in the electron shell. They are negatively charged.
• The protons are located in the nucleus. They are positively charged.
• The Neutrons are located in the nucleus. They have a neutral charge.
• The octet rule is that the valence shell of an atom can hold up to 8 electrons.
• Valence electrons are the electrons that are found in the outermost shell of an atom.
• The number of valence electrons is equal to the element's main group number.
• The columns of the periodic table are called groups and the rows of the periodic table are called periods.
• Atomic number indicates the number of protons or electrons.
• To determine the number of neutrons, subtract the atomic weight from the atomic number.
• The atomic weight indicates the number of protons and neutrons in the nucleus of an atom.
• The smallest particle found in elements is the proton.
• Oxygen and hydrogen are two elements that are made of molecules.
• A compound is a substance made up of two or more different elements chemically combined.
• Sodium, magnesium, and iron are examples of metals.
• Helium, boron, and sulfur are examples of non-metals.
• Two differences between elements and compounds are: Elements are pure substances, while compounds are made up of two or more elements.
• A mixture is different from a compound because it contains two or more different elements or compounds. A mixture can be separated into its components by physical means.
• Air is a mixture because it contains gases and particles that are not in equilibrium with each other and because it is constantly being exchanged with the atmosphere.
• Metals will lose electrons to become positive ions and non-metals will gain electrons to become positive ions.
• Metals lose electrons to become stable. Non-metals gain electrons to become stable.
• Once the number of protons and electrons are no longer equal the element will form an ion.
• Metals always form cations while non-metals form anions.
• Cations have a positive charge while anions have a negative charge.
• Lithium, aluminium, rubidium, and boron are examples of cations.
• Chlorine, phosphorus, and sulfur are examples of anions.
• Ionic bonding is a type of chemical bonding between a metal and a non-metal.
• Metals and non-metals assist each other in achieving full valence shells by donating and accepting electrons from each other and forming ionic compounds.
• Calcium and chlorine = calcium chloride
• Potassium and iodine = potassium iodide
• Aluminium and bromine = aluminium bromide
• Magnesium and oxygen = magnesium oxide
• Copper and fluorine = copper fluoride
• When table salt dissolves in water it is a physical change.
• When sugar dissolves in water it is a physical change.
• When silver tarnishes it is a chemical change.
• When pancakes cook it is both a physical and chemical change.
• When an apple is cut it is a physical change.
• When a tire is inflated it is a physical change.
• When heat changes water to steam it is a chemical change.
• When ice melts it is a physical change.