Chapter 2 Atoms, Molecules, Ions(Atomic weight, Isotopes, and periodic Table) 20-26جامعة الامير مقرن скачать в хорошем качестве

Chapter 2 Atoms, Molecules, Ions(Atomic weight, Isotopes, and periodic Table) 20-26جامعة الامير مقرن

Atomic Mass • Atoms have extremely small masses. • The heaviest known atoms have a mass of approximately 4 × 10 –22 g. • A mass scale on the atomic level is used, where an atomic mass unit (amu) is the base unit. ➢1 amu = 1.66054 × 10 –24 g Atomic Weight Measurement • Atomic and molecular weight can be measured with great accuracy using a mass spectrometer. • Masses of atoms are compared to the carbon atom with 6 protons and 6 neutrons (C-12). Symbols of Elements ➢ Elements are represented by a one or two letter symbol. C This is the symbol for carbon. ➢ All atoms of the same element have the same number of protons, which is called the atomic number, Z. It is written as a subscript BEFORE the symbol. ➢ The mass number is the total number of protons and neutrons in the nucleus of an atom. It is written as a superscript BEFORE the symbol. Isotopes • Isotopes are atoms of the same element with different masses. • Isotopes have different numbers of neutrons but the same number of protons. Atomic Weight • Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. • An average mass is found using all isotopes of an element weighted by their relative abundances. This is the element’s atomic weight. • That is, Atomic Weight = Ʃ [(isotope mass) × (fractional natural abundance)]. Note: the sum is for ALL isotopes of an element. Periodic Table • The periodic table is a systematic organization of the elements. • Elements are arranged in order of atomic number. • Unlike the way we write isotopes, the atomic number is at the TOP of a box in the periodic table. • The atomic weight of an element appears at the BOTTOM of the box. (They are not shown on this version of the Periodic Table.) • The rows on the periodic table are called periods. • Columns are called groups. • Elements in the same group have similar chemical properties. #chemistry #chemistry101 #generalChemistry #chapter2 #learning #exam #class #تسريبات #بنك_اسئلة #quiz #exam #education #تعليم #تجميعات #course #كيمياء #جامعة_الامير_مقرن #السعودية #مصر #ksa #egypt