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Summary
- Electrons, protons and neutrons are subatomic particles. Electrons are negatively charged, protons are positively charged and neutrons have no charge. The protons and neutrons are located in the nucleus of an atoms and electrons are outside the neutrons. Most of the mass of an atom comes from the necleus (ie. from protons and neutrons). The mass of an electron is about 1800 times less than that of s proton or a neutron
- Atomic number is the number of protons in an atom. Mass number is the number of protons and neutrons in an atom. An atom is identified by the number of protons.
- Isotopes are atoms of the same element (ie. same atomic number, so, same number of protons), but have different mass number (ie. different number of neutrons)
- When atoms lose electrons, a positive ion (cation) is formed. When atoms gain electrons, a negative ion is formed
- Ionic compound are composed of cations and anions; the cation is usually formed by metals when they lose electrons and the negative ions is usually formed by a non-metal or group of non-metals when they gain electrons. In ionic compounds, the attraction betwen the cation and anion is called the ionic bond.
- A molecular compound is usually composed of only nonmetals. The non-metals bond by sharing electrons, which is referred to as the covalent bond
- Ions that have only one atom are refferred to as monoatomic ions. The charge of group some common ions (group- 1A, 2A, VII A, VIA, VA ions and aluminum ion) can be determined using the periodic table. The name of monoatomic anions usually end with "ide".
- Transition metal ions are named with their charge written as a roman numeral within parentheses. Example, Fe3+ is named Iron(III)
- Polyatomic ions contain more than one atom. The names of polyatomic ions usually end with "ate" and "ite". The formula of polyatomic ions has be memorized or looked up and cannot be determined from the periodic table.
- The formula for an ionic compound should contain the lowest ratio of the respective cation and anion so that the overall charge is zero. For example: Ca3N2 contains three Ca2+ ions for every two N3- ions.
- Ionic compounds are named with the name of the cation followed by the name of the anion. For example, Ca3N2 is named calcium nitride, Fe3N2 is named iron(II) nitride.
- The name of the moelcular compounds use greek prefixes; for example, N2O4 is named dinitrogen tetroxide; CO is named carbon monoxide (notice that mono is dropped at the beginning of the name).
- If the anion name ends with "ide", the corresponding acid's name starts with "hydro" and ends with "ide"; If the anion name ends with "ate", the corresponding acid's name ends with "ic acid"; If the anion name ends with "ite", the corresponding acid's name ends with "ous acid".
