The National Eligibility Entrance Test is a crucial examination for all BDS and MBBS aspirants across India. The test is conducted by the NTA (National Testing Agency). The latest exam pattern for NEET includes two hundred multiple-choice questions, which contain four marks each. The questions consist of 11th and 12th standard syllabi from Biology, Chemistry, and Physics. Out of these 200 questions, candidates need to answer 180 of them.
Quite straightforward, right? However, general candidates have to ensure that they score a 50% in all these subjects to pass the exam. That is, you have to score at least 50% in Biology, Chemistry, and Physics respectively to pass your exam. Hence, one needs to be well-prepared in every subject if they want to pass the exam in a go.
To practice your knowledge, check out the MCQs on Structure of Atoms for NEET.
What is an Atom?
The smallest unit of an element is called an atom. An atom retains all the chemical properties of the element. The atoms of an element combine to form molecules. These molecules then interact to form liquids, gases, and solids. For instance, if you take water, it is composed of oxygen and hydrogen atoms. The atoms of Hydrogen and Oxygen combine to form water.
What are Atomic Particles?
An atom is made of three particles: neutrons, electrons, and protons. The centre of the atom is called the nucleus. It contains the neutrons are protons that are not charged and positively charged, respectively.
An atom’s outermost region has electron shells that contain the subatomic particles called electrons. The electrons are negatively charged particles. An atom would have different properties depending on the number of these basic particles and their arrangements.
To understand this better, you can take the example of hydrogen (H) atoms. A Hydrogen atom contains no neutrons, one electron, and one proton. These particles can be used for determining the mass and atomic number of Hydrogen.
- What is an Atomic Number?
An element with neutral atoms would contain electrons and protons of equal numbers. The number of protons states the atomic number (Z) of an element. This atomic number differentiates between elements. To understand this better, you can take the example of carbon. The atomic number (Z) of carbon is 6. This means one carbon atom has 6 protons.
However, the number of neutrons might vary to form isotopes. These are atoms of one element but with different quantities of neutrons. Besides that, the number of electrons might also be different in atoms of an element for forming ions (also known as charged atoms). If you take the example of Fe (Iron), it has its neutral state and 3, 2 ionic states.
- What is Atomic Mass Number?
An element’s mass number (A) is the sum of neutrons and protons in an atom. Here the mass of electrons is not considered while calculating the atomic mass number. This approximate atomic mass is also used for calculating the number of neutrons by subtracting the proton number from the atomic mass number. Neutrons and protons are one AMU (atomic mass unit). Hence, isotopes of an element can have different mass numbers but the same atomic number.
What is Atomic Structure?
An atom consists of a nucleus and electrons that are arranged around the nucleus. Hence, an element’s atomic structure refers to this constitution of nucleus and electron arrangement. Thus, the atomic structure includes neutrons, electrons, and protons.
The nucleus of an atom is made of neutrons and protons. The nucleus, in turn, is surrounded by electrons. The number of protons present in an atom’s nucleus determines its atomic number. Neutral atoms have electrons and protons in equal numbers. However, atoms of some elements can lose or gain electrons for increasing their stability. This newly charged entity is termed an ion.
However, no atomic structure is the same as different elements have different electrons and protons in their atoms. That is why different elements come with unique characteristics.
What is the Atomic Model?
Various scientists in the eighteenth and nineteenth centuries have attempted to demonstrate the atomic structure through atomic models. The most notable contributors to this field are scientists Niels Bohr, Ernest Rutherford, J. J. Thomson, and John Dalton. Models provided by each of these scientists have their own merits and demerits.
Although all models were pivotal for developing the atomic model we read today, John Dalton Atomic Theory is considered the most appropriate. So, let us read about it.
Atomic Theory By John Dalton
John Dalton was an English chemist who suggested that all matters are made of indestructible and indivisible atoms. He also stated that all atoms in an element are the same. However, atoms of different elements have different masses and sizes.
As per the atomic theory of Dalton, chemical reactions involve atom rearrangement to form products. Hence, he concluded that atoms are the small particles of an element responsible for chemical reactions.
Here are the findings of Dalton’s theory:
- Atoms are the smallest unit of matter, and every matter is made of atoms.
- An element would only have a single type of atom in them.
- Atoms are indivisible.
- Atoms have their constant mass, which differs across elements.
- Atoms cannot be destroyed or created but transformed from one form to another.
- Atoms are rearranged in a chemical reaction.
The atomic theory of Dalton successfully described the Laws of Chemical Reactions. These include Law of Reciprocal Proportions, Law of Multiple Proportions, Law of Constant Properties, and Law of Conservation of Mass.
Having a clear understanding of the structure of atoms is crucial for NEET aspirants as it is the most fundamental concept in chemistry. Atomic structure is further needed for understanding other chemistry concepts such as the Periodic Table, General Organic Chemistry, Chemical Bonding, and more to pass NEET with flying colours.