# Atoms Summary

• Atoms Summary
• Calculate Ar from relative abundance data
• The overall mass number of an element depends on;
• The percentage abundance of the different isotopes.
• The relative isotopic masses of the isotopes.
• We use data from a mass spectrometer to calculate the Ar of an element
• Mass Spectrometry tells us each relative isotopic masses and their abundancies
• Writing Formula
• The overall charge must be zero, so the ion charges must balance. Sum of positive charges= sum of negative charges
• Elements are represented by their symbols
• Charges are usually omitted from compound formula
• Diatomic molecules are when two atoms are bonded together
• The number of each atom, is shown in subscript. When there is multiple of a molecule, the number is put in front
• Binary compounds are compounds thats contain two elements only. To name, use the name of the first element, then change the ending of the second element to "ide"
• For Ionic compounds, metal ions always come first
• State symbols must be included: S) Solid, L) liquid, G) Gas, Aq) Solute in water (Aqueous)
• Structure
• Ion
• Negative ions have more electrons than protons.
• Positive ions have less electrons than protons
• Molecular polyatomic ions include
• Zinc Ion Zn
• Sulfate SO
• Carbonate CO
• Hydroxide OH
• Silver ion Ag
• Ammonium NH
• Nitrate NO
• Charge can be identified by group. Metals are positive. Non metals are negative
• Atom
• Electrons have a mass of 1/1836 and have a charge of -1, found in orbitals or energy levels
• Orbitals take up most volume in an atom
• Neutrons have a mass of +1 and a charge of 0, found in the nucleus
• Protons have a mass of 1 and charge of +1, found in nucleus
• These are uncharged as have same number of protons and electrons
• Mass is concentrated in the nucleus where you find nucleons
• Contains sub-atomic particles
• Balancing Equations
• Key Definitions
• Relative atomic (molecular) mass-
• Atomic masses are measured using the unified atomic mass unit, u  1 u = 1.660538782 x 10-27 kg
• The carbon-12 isotope is  the international standard all elemental masses are measured against
• The Ar is the weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon-12
• In comparrason to the Carbon-12 isotope
• Relative atom mass= abundance (intensity) X mass number (M/Z= mass to charge ratio). You then add each different isotope's calculation, then divide by the total abundance.
• All the data can be found using a Mass Spectrometer
• Isotope:
• These are atoms of the same element with the same number of protons but different numbers of neutrons. Also differing masses
• Relative isotopic mass, is the mass of an isoptope compared to 1/12 of the mass of carbon-12
• Atom
• Electrons have a mass of 1/1836 and have a charge of -1, found in orbitals or energy levels
• Orbitals take up most volume in an atom
• Neutrons have a mass of +1 and a charge of 0, found in the nucleus
• Protons have a mass of 1 and charge of +1, found in nucleus
• These are uncharged as have same number of protons and electrons
• Mass is concentrated in the nucleus where you find nucleons
• Contains sub-atomic particles