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Elements and compounds are the fundamentals of chemistry. They are the building blocks of matter. Element is a pure substance that is formed when similar kinds of atoms bond with each other. Compounds on the other hand are substances that are formed when two or more elements chemically combine with each other.
- Elements are entities that cannot be broken down into smaller substances.
- Compounds can be broken down into their constituent elements.
- Elements are formed of homogeneous atoms.
- Compounds are formed of heterogeneous molecules.
Read More: Carbon and Its Compounds
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Key Terms: Elements and Compounds, Elements, Compounds, Atoms, Molecules
What are Elements?
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An element is a pure substance having only one kind of atom present in its core. For example, Nitrogen is an element with the formula N2, it is a pure substance since it is only formed of nitrogen atoms.
- Elements are defined as the building blocks of matter.
- Elements, in the modern periodic table, are sorted on the basis of their increasing atomic number and comparable properties.
- To date, 118 elements have been discovered.
- Classification of Elements - metals, non-metals, and metalloids.
What are Compounds?
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A compound is formed when two or more elements combine together by chemical bonding in a fixed ratio. For example, common salt i.e. sodium chloride (NaCl) is a compound, it is formed when two elements- sodium and chlorine chemically bond with each other.
- The formula of a compound defines the composition of the compound.
- Compounds are classified as ionic and covalent compounds.
- When two metals or a metal and non-metal bond with each other, an ionic compound is formed.
- When two non-metals combine, covalent compounds are formed.
Examples of Elements
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The common examples of elements are-
| Element | Symbol | Atomic Number |
|---|---|---|
| Sodium | Na | 11 |
| Magnesium | Mg | 12 |
| Argon | Ar | 18 |
| Phosphorus | P | 15 |
| Calcium | Ca | 20 |
| Scandium | Sc | 21 |
| Iron | Fe | 26 |
| Cobalt | Co | 27 |
| Zinc | Zn | 30 |
| Neon | Ne | 10 |
| Copper | Cu | 29 |
Example of Compound
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The common example of compounds are-
| Compound | Symbol |
|---|---|
| Water | H2O |
| Hydrochloric Acid | HCl |
| Potassium Bromide | KBr |
| Tin (II) Chloride | SnCl2 |
| Sulfuric Acid | H2SO4 |
| Ammonia | NH3 |
| Ammonium | NH4 |
| Zinc Chloride | ZnCl2 |
| Zinc Oxide | ZnO |
| Sulfur Dioxide | SO2 |
| Sodium Bicarbonate | NaHCO3 |
Difference between Element and Compound
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The differences between elements and compounds are-
| Elements | Compounds |
|---|---|
| Elements are chemical substance that cannot be broken down into smaller particles either by chemical or physical methods. | Compounds are chemical compounds that can be broken down into its smaller constituent particles. |
| They are formed of similar kinds of atoms. | It is formed by combining different kinds of atoms. |
| They are classified as metals and non-metals. | They are classified as ionic and covalent. |
| Examples- hydrogen, helium, oxygen, etc. | Examples- methane, calcium carbonate, ethanol, etc. |
Things to Remember
- Elements are formed when similar kinds of atoms combine together.
- Compounds are formed when two or more kinds of atom bond with each other.
- Elements are chemical entities that cannot be broken down into simpler substances.
- Compounds are chemical entities that can be broken down into simpler elements.
- Compounds are heteronuclear molecules.
- 118 elements are known till this date.
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Sample Questions
Ques. Differentiate between elements and compounds. (2 marks)
Ans. Elements are substances having homogeneous molecules, whereas compounds are made up of heterogeneous molecules. Elements are neutral substances whereas molecules of compounds possess certain charges on them.
Ques. Why does a group of elements exhibit the same physical and chemical properties? (2 marks)
Ans. A group of elements exhibits the same chemical properties and physical properties because they possess the same number of valence electrons in their outermost shell also known as the valence shell.
Ques. Determine whether N2 is an element or a compound. (1 mark)
Ans. N2 is an element, not a compound because it is formed of only one kind of atoms i.e. nitrogen atoms.
Ques. What is the classification of elements and compounds? (2 marks)
Ans. Elements are classified into three types- metals, non-metals, and metalloids and compounds are classified according to the type of bonding in them which is ionic compounds and covalent compounds.
Ques. Which of the following is a compound? (1 mark)
(a) Hydrobromic Acid
(b) Oxygen
(c) Cadmium
(d) Yttrium
Ans. The correct option is (a.) Hydrobromic acid (HBr) is a compound.
Ques. Which of the following is an element? (1 mark)
(a) Hydrochloric Acid
(b) Ammonium
(c) Cadmium
(d) Sodium bicarbonate
Ans. The correct option is (c.) cadmium is an element.
Ques. Which of the following is not a compound? (1 mark)
(a) Acetone
(b) Bromine
(c) Ammonium chloride
(d) Methanol
Ans. The correct option is (b.) bromine is not a compound.
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