Presentation on theme: "Honors ch 4.3. An English scientist Discovered each element contains a unique positive charge in the nucleus The number of protons in the nucleus."— Presentation transcript:
How many protons and electrons are in: a. radon b. magnesium An atom of an element contains 66 electrons. What element is it? An atom of an element contains 14 protons. What element is it?
Dalton was incorrect about atoms being indivisible and stating that all atoms of an element are identical. (#2 and #5) All atoms of a particular element have the same number of protons and electrons but the number of neutrons in the nucleus can differ. Isotopes – atoms with the same number of protons but different numbers of neutrons
All Isotopes of a specific element have the same chemical behavior (determined by electrons) Isotopes are identified with a mass number Mass number = atomic # + # neutrons
In nature most elements are found as a mixture of isotopes Ex: copper – two types found naturally - 29 protons and 34 neutrons - 29 protons and 36 neutrons Cu – 63; Copper – 63, 63 Cu, 63 29 Cu Cu – 65; Copper – 65, 65 Cu, 65 29 Cu
Atoms are measured in amu (atomic mass units). (based on carbon -12) 1 amu is almost equal to 1 proton or neutron Atomic mass – the weighted average mass of the isotopes of that element. Because isotopes have different masses, the weighted average mass is NOT a whole number.