Atoms and Compounds

117 elements
1. All substances are made of atoms
  1. Atoms consist of a small nucleus surrounded by electrons
2. when elements react, their atoms join with atoms of other elements
  1. Compounds are formed (2 or more elements)
Nucleus contains protons and neutrons(particles)
1. Protons have a positive charge and neutrons have no charge
  1. Atomic number(proton number)- number of protons in an atom of an element
    1. Elements arranged in atomic no. in the periodic table
  2. Atomic number also the number of electrons
Electrons are tiny negatively charged particles
1. move around the nucleus
2. Number of protons is equal to the number of electrons
  1. No overall charge
  2. Charges are equal and opposite(proton+1 electron-1)
Mass number- total no. of particles in the nucleus of an atom
1. Number of neutrons + number of protons
Atoms of the unreactive noble gases(group 0) all have very stable arrangement of electrons
1. Electrons are in energy levels that are represented as shells
  1. the elements in the same group have the same no. of electrons on their outer shell
  2. Occupy lowest shell first
Compounds of metals bonded to non-metals have ionic bonds
1. compounds of non-metals have covalent bonds

Zusammenfassung der Ressource

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