atomic bonding ✅

• an atom is the smallest particle of an element that can exist
• an atom is the building blocks of matter
• atoms of different elements are different in sizes
• to represent atoms of an element:

  • commonly used are circles, with symbols written in the circle to represent the atoms of the element
  • or using spheres of different colours and sizes
• atoms are usually made up of 3 types of sub-particles:

  • protons (Positively charged)
  • neutrons (no charge)
  • electrons (negatively charged)
• a proton’s relative mass to a carbon element is 1, its relative charge is +1 and is found in the nucleus
• a neutron’s relative mass to a carbon element is 1, its relative charge is 0 and is found in the nucleus
• an electron’s relative mass to a carbon element is 1/1840, its relative charge is -1 and is found moving around the nucleus at high speeds
• protons and neutrons are almost equal in mass and are assigned a relative mass of 1 atomic mass unit each
• the mass of an electron is so small that it is considered negligible
• the mass of an atom is based on the number of protons and neutrons only
• number of protons in an atom can be found in the periodic table
• top is the atomic/proton number

  middle is the symbol of elements

  bottom is the mass/nucleon number

  
• the atomic/proton number refers to the number of protons
• each atom has as unique proton number
• atoms of different elements have different number of protons
• in an atom, no. of electrons is equal to the no. of protons and hence an atom is considered electrically neutral, it has no charge
• mass/nucleon number is the number of protons and nucleons
• total number of particles in the nucleus (protons and neutrons) is the nucleon number 
• since the mass of an electron is considered negligible, the mass of an atom is equal to the sum of protons and neutrons only 
• each atom can be represented by its own nuclide notation
• A refers to the mass/nucleon number

  Z refers to the atomic/proton number

  X refers to chemical symbol

  
• electrons are arranged around the nucleus in electron shells, each shell is associated with a specific energy level and the shell nearer to the nucleus is lower in energy level
• the first shell can hold up to 2 electrons, it is called a duplet structure
• the second to fourth shell; can hold up to 8 electrons, its called an octet structure 
• atoms tend to be stable when they have 8 electrons in their outermost shell 
• the electrons in the second to fourth shell should be paired 
• electrons in the outermost shell are known as valence electrons or outermost electrons 
• in any chemical reaction, only the electrons take part in the reaction, as such, elements with the same number of valence electrons have the same chemical properties 
• electrons move rapidly and at relatively great distances from the tiny nucleus. Hence, it is not possible to pinpoint exact locations of the electrons within an orbit at any one time 
• most of the atom is empty space
• isotopes are atoms of the same element with the same number of protons but different number of neutrons 
• isotopes have similar chemical properties because they have the same no. of valence electrons
• isotopes have slightly different physical properties because they have different no. of neutrons
• isotopes may present in different abundance, hence relative atomic mass is an average of the masses of the isotopes based on their percentage abundance 

  -the relative atomic mass shown in Periodic Table takes into account all these isotopes and their relative abundances 
• formula for average atomic mass: % abundance x mass of isotope A + % abundance x mass of isotope B
• chemical bonds are formed for atoms to achieve a stable noble gas electronic configuration (full valence electron shell)
• chemical bonds are formed by:

  • loss of valence electrons (by metal atoms)
  • • gain of electrons (by non-metal atoms)
  • • sharing of valence electrons (between non-metals) 
• ionic bonding is strong electrostatic forces of attraction between oppositely charged ions (cations and anions)

  Formed when: A metal atom transfers its valence electrons to non-metal atom(s)
• the attraction between the positive ion and negative ion is called the ionic bond