Atomic Structure All natural and most synthetic substances on earth are made from the ninety naturally occurring chemical elements. An atom is the smallest particle into which an element can be divided while still retaining the chemical characteristics of that element (fig 3. 1). The nucleus, at the center of the atom contains one or more particles with a positive electrical charge(protons fif and usually some particles of similar mass that have no charge(neutrons
1、早期的太阳系 The Early Solar System Billions of years ago, out of a swirling mass of gas and dust, evolved a system of varied planets hurtling around a nuclear-powered star-our solar system. One of these planets, and one only, give rise to complex life forms. Over time
Chapter One Nitrogen Family(Group V) Central contents 1. Know the general properties of elements of the nitrogen group and inert electron pair effect 2. Know the reactions of ammonia, understand the thermal decomposition trend of ammonium salts 3. Know the properties of nitrous acid and nitrites; understand the structure of nitric acid and nitrate radical; understand the thermal decomposition trend of nitrates
2-1 Preface 2-2 Fluid Static Pressure and Its Characters 2-3 Differential Equation of Fluid Equilibrium 2-4 Equilibrium Fluids in Gravity Field 2-5 Calculation and Measure of Static Pressure 2-6 Relative Equilibrium of Liquid 2-7 Total Pressure Acting on Plane of Static Fluids 2-8 Total Pressure Acting on Curved Surface of Static
2.1 scalar and vector quantities 1. scalar Physical concepts that require only one numerical quantity for their complete specification are scalar quantities. 2. vector Vector quantities require for their complete specification a positive quantity, called the magnitude of the vector and the direction otice:Not all things with a magnitude and direction are vectors
