Atomic structure + isotopes, Compunds, Formula + Equations

• Dalton's atomic theory states that atoms are tiny particles made of elements, cannot be divided, all the atoms in a element are the same, and atoms of one element are different to those of other elements.
• Thompson discovered that electrons have a negative charge, can be deflected by magnet and electric field, and have very small mass.
• The plum pudding model suggests that atoms are made up of negative electrons moving around in a sea of positive charge.
• The mass of a proton and a neutron is taken as 1.0 u.
• In a mass spectrometer, the sample is made into positive ions, which then pass through the apparatus and are separated according to mass to charge ratio.
• Mass spectrometry is used for identifying unknown compounds, finding the relative abundance of each isotope of an element, and determining structural information.
• Both relative molecular mass and relative formula mass can be calculated by adding the relative atomic masses of each of the atoms making up the molecule or the formula.
• A computer analyses the data and produces a mass spectrum.
• Rutherford's proposal after the gold leaf experiment states that most of the mass and positive charge of the atom are in the nucleus, electrons orbit the nucleus, most of atom’s volume is the space between the nucleus and the electrons, and overall positive and negative charges must balance.
• The current model of the atom suggests that protons and neutrons are found in the nucleus, electrons orbit in shells, nucleus is tiny compared to the total volume of atom, most of atom’s mass is in the nucleus, and most of the atom is empty space between the nucleus and the electrons.
• The charge of a proton is 1+.
• The charge of an electron is 1-.
• A particle with the same mass as a proton is a neutron.
• Protons and neutrons make up most of atom’s mass.
• The charge of a carbonate ion is -2 → CO 3 2-.
• Metals usually gain electrons.
• The charge of a hydroxide ion is -1 → OH -.
• To calculate an empirical formula, divide the amount of each element by its molar mass, divide the answers by the smallest value obtained, and if there is a decimal, divide by a suitable number to make it into a whole number.
• The charge of a sulfate ion is -2 → SO 4 2-.
• Group number indicates a vertical column in the periodic table.
• Non-metals generally gain electrons.
• An empirical formula is the simplest whole number ratio of atoms of each element present in a compound.
• The charge of an ammonium ion is +1 → NH 4 +.
• The elements beryllium, boron, carbon and silicon do not tend to form ions due to the high energy required to transfer outer shell electrons.
• Molecular ions are covalently bonded atoms that lose or gain electrons.
• Group number is equal to the number of electrons in the outer shell.
• The charge of a nitrate ion is -1 → NO 3 -.
• Neutrons have no impact on the chemical reactivity of isotopes of the same element.
• When calculating mass number, two assumptions are made: the contribution of the electron is neglected and the mass of the electron is assumed to be zero.
• The unit used to measure atomic masses is the Unified atomic mass unit, u.
• Reactions involve electrons, isotopes have the same number of electrons in the same arrangement.
• Ions are charged particles that are formed when an atom loses or gains electrons.
• Isotopes are atoms of the same element with different numbers of neutrons.
• The relative isotopic mass is the same as the mass number.
• Mass number is calculated as the sum of the number of protons and the number of neutrons.
• The charge of an ion is negative when electrons are gained.
• Relative atomic mass is the weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12.
• The number of neutrons in an atom can be calculated by subtracting the atomic number from the mass number.
• Relative isotopic mass is the mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12.
• The atomic number is represented by the letter Z.