Chemistry Chapter 1

Chemistry Chapter 1

1. 1.1

   • Alll substances are made up of atoms
   • An element is a substance composed of only one type of atom
     • Iron is an element and consists of only ion atoms
   • An element cannot be broken down into anything simpler
   • Elements are found in the peridic table of elements
   • Groups are the vertical columns
     • Each group contains elements with similar properties
   • Compounds contain more than one type of atom

2. 1.2

   • There are three particles making up the atom
     • Protons
       • Have a positive charge, mass of 1
     • Neutrons
       • Have no charge, mass of 1
     • Electrons
       • Have a negative charge, mass of less than one
   • The number of protons (+) and the number of electrons (-) in an atom are equal, so the charges balance each other out
     • As a result an atom has no overall charge
   • Atoms are arranged in order of increasing atomic number
     • This is the smaller number
     • It tells you the number of protons in the nucleus
       • This is also equal to the number of electrons in the shells
   • The mass number/atomic mass is the mass of the nucleus
     • It is the bigger number
     • It is the sum of the protons and the neutrons

3. 1.3

   • Electrons fill up the shells around the atom's nucleus in a set pattern
     • They must fill in the inner most shell first before starting the next shell
     • Shell 1 can hold 2 electrons. Shell 2 can hold 8 electrons. Shell 3 can hold 8 electrons. Shell 4 can hold 18 electrons
     • Atoms with the same number of electrons in their outmost shell belong in the same group in the periodic table
       • So group 1 elements have 1 electron in their outmost shell
   • The number of electrons in the outmost shell of an element's atoms determins the way that element reacts
   • Atoms of the unreactive noble gases in group 8/0 all have stable arrangements
     • All of their electron shells are full
   • It is the atomic number(smaller number) that tells you how many electrons to put in the electon shells
   • Isotope
     • Elements are made up from one type of atom, but there can be different forms of the atom in the element
     • Although atoms of the same element always have the same number of protons, they may have a differnt number of neutrons.
     • Change in neutrons but not the atomic number

4. 1.4

   • Compounds are shown by a formula
     • This tells us what the different elements are in that compound
       • CaCO3 is a compound that contains 3 different atoms: Ca, C and O
   • Every atom is trying to become stable
     • hey are trying to complete a full outer shell
       • They can achieve this by:
         • Losing electrons
         • Gaining electrons
         • Sharing electrons
   • Ionic bonding is the bonding between a metal ion and a non-metal ion
     • The metal loses electrons to become positivley charged
     • The non-metal gains electrons to become negatively charged
   • Convelant bonding is the sharing of electrons to form molecules
     • This happens between two non-met
       • Lots of other non-metals do it aswell