[Chemistry Class Notes] on Calcium Pdf for Exam

Calcium is an alkaline earth metal. Group 2 elements of the modern periodic table are known as alkaline earth metals (except Beryllium). Calcium being an alkaline earth metal, it forms a dark oxide-nitrate layer due to its high reactivity and when exposed to the air. Its physical and chemical properties are most similar to its heavier homologs strontium and barium. Sir Humphry Davy discovered calcium in 1808. Calcium is found to be the most abundant metal and when talking about the human body it is the fifth most abundant element in the human body. In the physiological and biochemical processes of organisms and cells, calcium ions have an important role as electrolytes. There are various uses of calcium and it is one of the most important chemical elements.

Calcium Element

The chemical symbol of calcium is ‘Ca’.Its atomic number is 20 and its atomic mass is 40.078 g/mol.

The location of calcium elements in the modern periodic table is the 2nd group,4th period, and ‘s’ block. Its electronic configuration is ArAr4s². At 20°c, this element is present in solid-state. It has a melting point of 842°c and a boiling point of 1484°c. The density of calcium is 1.54 gm/cm³.Important isotopes of calcium include 48Ca, 46Ca, 44Ca, 43Ca, 42Ca, and 40Ca.CAS number for calcium is 7440-70-2.

Calcium Symbol

Atomic Structure of Calcium

The nuclear composition of an atom of calcium-40 (atomic number: 20), the most common isotope of this element consists of 20 protons and 20 neutrons. 20 electrons occupy available electron shells (rings).

• A number of Energy Levels: 4

• First Energy Level: 2 

• Second Energy Level: 8 

• Third Energy Level: 8 

• Fourth Energy Level: 2

• So we can see it has 2 electrons in its valence shell, hence its valency is 2. The crystal structure of calcium is cubic. The atomic data of calcium is as follows:

• Covalent radius (Å):  1.74

• Electron affinity:  2.369 (kJ mol−1)

• Electronegativity:  1.00 (Pauling scale)

Atomic Data of Calcium

Ionisation Energies (kJ mol−1)

Uses of Calcium

1. The biological use of calcium is to provide strength and structure to the skeleton. It is vital for the maintenance of bones and teeth.

2. Calcium ions on bone surfaces interact with those present in the bodily fluids, therefore enabling ion exchange, which is essential in maintaining the balance of calcium in the blood and bone.

3. Calcium circulating in the blood is involved in several vital processes including coagulation, nerve signal transmission, hormone signaling, and muscle contraction.

4. Calcium may be used as a reducing agent in the process of metal extraction.

5. Calcium is also used in the production of some metals, as an alloying agent.

6. Calcium carbonate is used to make cement and mortar and also in the glass industry.

Properties of Calcium

Properties of calcium can be categorized as physical and chemical.

1. Physical Properties of Calcium

These are those properties that can be observed using our senses such as colour, lustre, freezing point, boiling point, melting point, density, hardness, and odour. These are observed without changing the substance into another substance. They are:

• Colour: Silvery-white metallic
• Phase: Solid
• Hardness: Relatively soft metal
• Crystalline structure: Cubic
• Ductility: It can be beaten into extremely thin sheets. It can be pressed, rolled, and cut
• Malleability: Capable of being shaped or bent
• Melting point: Melting point is 842°C
• Boiling point: Boiling point is 1484°C

2. Chemical Properties of Calcium

These are only observable during a chemical reaction. These properties determine how calcium behaves when changing from one substance to another or when reacting with other substances. They are:

• Chemical Formula: Ca
• Oxidation: Used as a deoxidizer in steel
• Isotopes: Six
• Compounds: Compounds include limestone, marble, gypsum, etc.
• Flammability: When heated in air or in oxygen it ignites
• Reactivity with water: Reacts with cold water rapidly at first, but the reaction is then slowed due to the formation of a film of Calcium hydroxide – [Ca(OH)_{2}]
• Reactivity with acids: Highly reactive

Calcium Compounds

Important compounds of calcium are:

1. Calcium oxide or Quicklime (CaO)

2. Calcium hydroxide or Slaked lime  [(Ca(OH)_{2})]

3. Calcium Carbonate  [(CaCO_{3})]

4. Calcium Sulphate or Plaster of Paris [(CaSO_{4} . frac{1}{2}H_{2}O)]

Facts About Calcium

1. Humans have known about calcium and its compounds before the Greeks and Romans.

2. Romans made use of lime in their concrete and termed it “Calx.”

3. Davy could separate pure calcium in 1808. He was the original chemist to do so.

4. It turns tougher as a silver-coloured metal once it is refined.

5. Calcium is used in fireworks to add orange colour.

Calcium in Living Organisms

Calcium is found in all living and dead organisms since it is necessary for life. Aquatic animals’ shells, eggshells, and snail shells are all made up mostly of calcium carbonate, which dissolves in acid. Aside from skeletal activities, the Ca²⁺ ion is important in signal transduction pathways, muscle function, neurotransmission, fertilization, and enzymatic activity in mammals and many species. Calcium is also found in the membrane, cell wall, and vacuole of plants. Coral reefs, which are mainly calcium carbonate, are one of the most important calcium deposits. Over the course of their lives, coral secretes calcium carbonate and ultimately dies, allowing new coral to grow on top of their calcium carbonate framework. These calcium deposits build into huge reefs over a long period of time, some of which can be seen from space. Photosynthesis in sea plants is preferred in these areas due to the abundance of sunshine and minerals such as calcium, allowing fish and other marine life to thrive. Calcium phosphate makes up the majority of human bones. Cow milk is likewise high in calcium phosphate, which is why human society encourages youngsters and others who are at risk of osteoporosis to consume milk.

Osteoporosis

The National Institutes of Health estimates that half of all women over 50 and a quarter of all males over 50 will break a bone as a result of osteoporosis. Osteoporosis is most common in postmenopausal white and Asian women. In women with osteoporosis, about 25% will have a vertebral deformity, and 15% will fracture their hip. Men can also break their hips due to osteoporosis, albeit not as frequently as women. Hip fractures are linked to an increased risk of mortality in the first year following the break. Osteoporosis is caused by a combination of circumstances:

• Not enough calcium in the diet.

• Age over 50.

• Small, thin body build.

• Family history of osteoporosis.

• Smoking.

• Use of certain medications such as breast cancer treatments, seizure medications, steroids.

Symptoms of Osteoporosis

Bone loss symptoms do not appear until osteoporosis has progressed. Osteoporosis may not cause any symptoms at all in its early stages. As osteoporosis progresses, the following symptoms may appear:

• Breaking bones easily.

• Back pain.

• Stooped posture.

• Gradual loss of height.