Q- How are atoms of different elements distinguished from
one another? In other words, how do we distinguish a
helium atom from a carbon atom?
A- Their number of p rotons , indicated by the atomic number
Let’s look at helium , He. It has an atomic number of 2, which means that is has 2 protons in it’s nucleus.
Atomic Structure Here are the basics; you need to know these. 1 H 1.0076 Hydrogen Atomic Number ( Z ) : the number of protons (p + ) Atomic Mass : the number of protons (p + ) + the number of neutrons (n 0 ) ▪ measured in atomic mass units (amu) which is one twelfth the mass of a carbon-12 atom. ▪ the mass of electrons (1/1860 p + ) is negligible. Number of Neutrons : the atomic mass - the atomic number Atomic Number Atomic Symbol Atomic Mass
Lets practice! Find the missing information? 8 15.999 amu O 2 2 He 39.948 amu 18 Ar Neutrons Electrons Protons Atomic Mass Atomic # Element
Examples: 6.02 x 10 23 Ca 2+ Ion Calcium ion 6.02 x 10 23 H 2 O Molecule Water 6.02 x 10 23 N Atom Atomic nitrogen Representative Particles in 1.00 mol Chemical Formula Representative Particle Substance
Solve Representative Particles in 1.00 mol Formula Unit Representative Particle Substance Molecule C Carbon Molecule C 12 H 22 O 11 Sucrose Molecule CaF 2 Calcium Fluoride Molecule N 2 Nitrogen gas