Atoms and elements

• The atom is composed of protons , neutrons and electrons
• Atoms have a nucleus containing protons and neutrons .
• Electrons move around the nucleus of the atom
• All atoms have a nucleus . The nucleus is always positively charged as it contains protons which have a positive charge and neutrons which do not have a charge .
• The nucleus contains more than 99% of the mass of the atom
• The total number of protons in an atoms nucleus must be the same as the total electrons in the outer shells
• Electrons in atoms always orbit the nucleus and have a negative charge
• Atoms are always neutral because the positive charge from protons cancels out the negative charge from electrons
• The nucleus of a atom of an element may contain different number neutrons .
• The diameter of the atom is about 10 to the power of -10 . Whereas the diameter of the nucleus is much smaller at around 10 to the power of -15
• An electron will move from a lower to a higher orbit if it absorbs electromagnetic radiation .
• An electron will move from a higher to lower obit if it emits electromagnetic radiation.
• Is an image of an electron absorbing electromagnetic radiation

  
• Is an image of an atom if it emits electromagnetic radiation

  
• The atom is the smallest part of an element that can exist
• All substances are made of atoms
• Atoms are very small with a radius of 0.1 nm
• An element contains only one type of atom
• Elements are found on the periodic table
• There are about 100 elements.
• An isotope is the same element with a different number of nuetrons