The elements of Group 2 Shown below, including Sodium and Potassium, are called alkaline earth metals.
- Be (Beryllium used for making containers of atomic fuel, also as a window material in x-ray apparatus)
- Mg (chlorophyll, a compound of Magnesium, helps in photosynthesis.)
The elements shown in the list above are in decreasing solubility of sulphates in water and in increasing order of thermal stability of carbonates.
Alkaline Earth Metals tend to be soft and highly reactive metals, because they have only two electrons in the outer shell.
Colors imparted to flame by alkaline earth metals, some of these are used in firework displays to be more colorful:
- Sodium golden yellow
- Potassium pink
- Calcium brick red
- Barium green
- Strontium crimson red
Location in the Periodic Table
Acid is any substance that can donate a hydrogen ion (H+) is an acid.
Therefore, an acid increases the hydrogen ion concentration.
Examples: Vinegar, Citrus Fruits, Stomach Acid (HCl)
Base is any substance that can accept a H+ ion. A base therefore decreases the H+ion concentration.
Examples: Sodium Hydroxide, Ammonia
- Acids taste sour
- Acids react strongly with metals (Zn + HCl)
- Strong Acids are dangerous and can burn your skin
- Bases taste bitter
- Bases feel slippery
- Strong bases are very dangerous and can burn your skin
ACID + BASE = SALT + WATER
When acids and bases are added to each other they react and neutralize each other . Neutralization results in the decomposition to salt and water and sometimes a gas also.
Acid Base Gas Salt Water
HCl + NaHCO3 —> H2CO3 + NaCl + H2O
The acidity or basicity of a solution is measured by pH.
The pH of a substance is the negative log of H+ ion concentration. It is written as
pH = -log [H+]
Units of pH
When measuring pH, [H+] is in units of moles of H+ per liter of solution.
The pH scale
pOH is the opposite of pH
An indicator is a special type of compound that changes color as the pH of a solution changes, thus telling us the pH of the solution.
The half-life period refers to the time it takes a radioactive material to disintegrate to half its original amount of radioactivity.
The Half-life Period is given by the formula
where = disintegration constant
The half-life is not dependent on the amount of radioactive element, that is, the size of the material does not matter. Only the amount of radioactivity at any given time that matters.
Note: Longer the half-life period of a radioactive element, the more stable it is.
One of the most common uses of the half-life measurement is in the method of dating fossils. Depending on the amount of radioactivity available now, it is possible to estimate how old a fossil is.