Nucleus has a radius of about 10-13 cm. An atom has a radius of about 10-8 cm or 1 Å (angstroms). If an atom were the size of a football stadium, with the electrons out around the upper deck, the nucleus down at midfield would be smaller than the coin flipped at the start of the game. 3.2 Atomic Number and Mass Number Atomic number (Z): Number of protons in a nucleus of an atom is called atomic number (Z). Z is characteristic of an element. An atom of oxygen always has protons and atomic number equal to eight. Mass Numbers (A): Number of neutrons and protons together in a nucleus of an atom is called mass number (A). 3.3 Isotopes and Atomic Masses Atoms of an element having different number of neutrons in the nucleus are called isotopes. These atoms of the same element (same Z) have different atoms different Mass Number (A) values. Isotopic symbol: Element symbol (X) found on the periodic table with number of protons or atomic number (Z) written as left subscript, and mass number (A), total of number of protons and neutrons written as left superscript. A 12 X E.g carbon-12: C Z 6 or simply written as 12C because once atomic symbol is known atomic number could be found easily from the periodic table. Carbon-12 with natural abundance of 99.90% Carbon-13 with natural abundance of 1.10% The average atomic weight of carbon is listed as 12.0107 hydrogen-1 isotope 1 2 3 H H H has 1 proton and 1 electron 1 1 1 hydrogen-2 isotope (deuterium) hydrogen-1 hydrogen-2 hydrogen-3 has 1 proton, 1 neutron, 1 electron. Hydrogen-3 isotope (tritium) has 1 proton, 2 neutrons, and 1 electron. Average Atomic Mass (A.A.M) Average atomic mass (A.A.M)for an element which is reported on the periodic table is calculated based on the masses of isotopes and their relative composition.
Nucleus has a radius of about 10-13 cm. An atom has a radius of about 10-8 cm or 1 Å (angstroms). If an atom were the size of a football stadium, with the electrons out around the upper deck, the nucleus down at midfield would be smaller than the coin flipped at the start of the game. 3.2 Atomic Number and Mass Number Atomic number (Z): Number of protons in a nucleus of an atom is called atomic number (Z). Z is characteristic of an element. An atom of oxygen always has protons and atomic number equal to eight. Mass Numbers (A): Number of neutrons and protons together in a nucleus of an atom is called mass number (A). 3.3 Isotopes and Atomic Masses Atoms of an element having different number of neutrons in the nucleus are called isotopes. These atoms of the same element (same Z) have different atoms different Mass Number (A) values. Isotopic symbol: Element symbol (X) found on the periodic table with number of protons or atomic number (Z) written as left subscript, and mass number (A), total of number of protons and neutrons written as left superscript. A 12 X E.g carbon-12: C Z 6 or simply written as 12C because once atomic symbol is known atomic number could be found easily from the periodic table. Carbon-12 with natural abundance of 99.90% Carbon-13 with natural abundance of 1.10% The average atomic weight of carbon is listed as 12.0107 1 1 H 2 1 H 3 1 H hydrogen-1 hydrogen-2 hydrogen-3 hydrogen-1 isotope has 1 proton and 1 electron hydrogen-2 isotope (deuterium) has 1 proton, 1 neutron, 1 electron. Hydrogen-3 isotope (tritium) has 1 proton, 2 neutrons, and 1 electron. Average Atomic Mass (A.A.M) Average atomic mass (A.A.M)for an element which is reported on the periodic table is calculated based on the masses of isotopes and their relative composition.