Atomic Structure and Isotopes

Particle Relative Mass Relative Charge PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”) ELECTRON – negative, mass nearly nothing Particle Relative Mass Relative Charge Proton 1 Neutron Electron 1/1850 -1

number of protons is the same as the number electrons 2 4 MASS NUMBER = number of protons + number of neutrons SYMBOL ATOMIC NUMBER = number of protons (proton number) For a neutral atom the number of protons is the same as the number electrons

U Example 238 U is the symbol for uranium 92 p = 92 therefore there are 92 protons m = 238 so there is 238 nucleons (m – p) 238 – 92 = 146 neutrons

How many protons, neutrons and electrons? Mass and atomic number How many protons, neutrons and electrons? 1 11 16 H B O 1 5 8 23 35 238 Na Cl U 11 17 92

Isotopes:- The three isotopes of oxygen An isotope is an atom with the same number of protons but a different number of neutrons: O 8 16 17 18 Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more. Notice that the mass number is different. How many neutrons does each isotope have?

Which one is not an isotope of hydrogen?

Isotopes of Carbon C 6 12 13 14 Each isotope has 6 protons – if it didn’t then it just wouldn’t be carbon any more. Notice that the mass number is different. How many neutrons does each isotope have?