All metals have a tendency to lose electrons and form metal ions. In other words, all metals are good reducing agents and easily oxidise themselves.
M →→ Mn+ + ne-
The reactivity series of elements can be shown in another way, which includes oxidation reaction of each metal to the respective metal ion. It gives information regarding the reducing power of the metal atom and the oxidation number of the metal ion.
Exothermic and endothermic reactions All processes can be classified into one of two categories: exothermic and endothermic. In an exothermic process, energy is released, while in an endothermic process, energy is stored. This section will specifically cover exothermic and endothermic chemical reactions, but almost any process can be described as releasing or storing energy.
The concept of giving off or storing energy can sometimes be a bit confusing, so let's go over some of the basic types of energy that you'll encounter in your chemistry class, and what it means to give off and store each type of energy.
Heat: Heat energy is the energy that accompanies temperature changes. If heat energy is being released then the reaction from which it is released will become hotter. If heat energy is being stored, then reaction will become colder.
Light: If light energy is being given off, then the reaction will glow. If it's being stored, then the reaction will seemingly proceed on its own without any catalyst present without any heat being evolved or absorbed.
Mechanical energy: If mechanical energy is being stored, then the volume and/or pressure of the reaction will get smaller. If mechanical energy is being given off, then the opposite will be true.
The most common change in energy that you'll witness in your chemistry class will be changes in heat energy. It can be measured with a bomb calorimeter. Energy released or stored in a reaction will often be expressed written as ΔH, or a change in enthalpy. A positive ΔH means that energy is stored and the reaction is endothermic. A negative ΔH means that energy is released and the reaction is exothermic. It is usually expressed in kilojoules (kJ) or joules (J).