chemistry key concepts

• Atomic number = number of protons
• The mass number is the total number of protons and neutrons.
• Isotopes are atoms with different numbers of neutrons but the same number of protons and electrons
• Ionic compounds have high melting points due to strong electrostatic forces between oppositely charged ions.
• Group 1 elements (alkali metals) all have one electron in their outermost shell.
• Electrolysis involves passing an electric current through molten or dissolved ionic substances.
• In electrolysis, positive ions move towards the negative electrode (cathode), while negative ions move towards the positive electrode (anode).
• Displacement reactions occur when a more reactive element replaces a less reactive element in a chemical reaction.
• Magnesium carbonate is insoluble in water but soluble in dilute acids like HCl.