Isotopes Are Atoms Of The Same Element With Different Numbers Of

Also, what are 2 isotopes of the same element different? An isotope is one of two or more forms of the same chemical element. Different isotopes of an element have the same number of protons in the nucleus, giving them the same atomic number, but a different number of neutrons giving each elemental isotope a different atomic weight. What are isotopes? A.) Atoms of the same element that have a different number of protons B.) Atoms of the same element that have a different number of neutrons C.) Atoms of different elements that have the same number of neutrons D.) Atoms that are unstable. Isotopes Atoms of the same element that have different masses due to different numbers of neutrons in 1932 that James Chadwick found evidence of neutrons which are uncharged subatomic particles with a mass very similar to that of protons. The Atom Atomic Number and Mass Number Isotopes. Terms in this set (38) Atomic Therory-Atoms are building blocks of elements-Similar atoms in each element-Different from atoms of other elements-Two or more different atoms bond in simple ratios to form compounds.Atoms of the same.

The Technical Details: Chemistry

Isotopes Are Atoms Of The Same Element With Different Numbers Of

Composition of an Atom

Atoms, which are the basic, fundamental unit of all matter, can differ greatly from one another. Although atoms are too small to see without using high-powered microscopes, they are composed of even smaller particles: protons, neutrons, and electrons.

Electrons, which are extremely light, negatively-charged particles, orbit around a central mass–the nucleus of an atom. Atoms may gain or lose electrons, which change the charge of the atom (creating ions). However, the atom remains the same element whether it has a positive, negative, or neutral charge.

The small, dense nucleus (or center) of the atom contains the other components–the protons and neutrons. Protons are positively charged particles, and the number of protons is always fixed for a particular element. In other words, the number of protons is what gives each element its unique, individual identity. For example, a carbon atom has six protons, but an atom with only five protons is boron while an atom with seven protons is the element nitrogen.

Neutrons are neutral - they have no charge. Isotopes are atoms of the same element that have a different number of neutrons. Although isotopes of the same element are twins when it comes to reactivity, the different number of neutrons means that they have a different mass. Certain isotopes are more abundant in some materials than others since some physical and chemical processes “prefer” one isotope over another. These differences in isotopic abundance are used as “labels” to identify the different sources of CO2 found in an atmospheric CO2 sample. NOAA atmospheric scientists use these isotopic labels to determine what percent of that carbon was derived from fossil fuels, the terrestrial biosphere, or from the ocean.

Isotopes of Carbon

Carbon isotopes come in three forms. By far the most common isotope of carbon is carbon-12 (12C), which contains six neutrons in addition to its six protons. The next heaviest carbon isotope, carbon-13 (13C), has seven neutrons. Both 12C and 13C are called stable isotopes since they do not decay into other forms or elements over time. The rare carbon-14 (14C) isotope contains eight neutrons in its nucleus. Unlike 12C and 13C, this isotope is unstable, or radioactive. Over time, a 14C atom will decay into a stable product.

The vast majority of all carbon found on Earth is 12C. Almost 99% of all carbon on Earth is of this form. While only approximately 1% of all carbon on Earth is of the 13C isotopic form, 14C is still much rarer. Only one out of every trillion carbon atoms is 14C.

To gain an idea of how few 14C atoms there are compared to 12C, let's compare one to one trillion. A trillion is a million millions. If you lined up a trillion one dollar bills, it would stretch almost from the Earth to the sun!

Contents

  • Atomic number and Mass number
  • Isotopes

Atom

An atom is the smallest particle of an element which can take part in chemical reaction. Atom consists of three fundamental particles i.e. proton, neutron and electron. Atoms of same elements are similar in properties whereas atoms of different elements are different in properties. Example:- ‘H’ represent the atom of hydrogen.

Proton is positively charged and electron is negatively charged particle. In an atom, number of protons = number of electrons. Hence, the net charge present in an atom is zero i.e. a free atom is chargeless.

Atomic number and Mass number

Atomic number :
  • Atomic number is the number of protons present in an atom.
  • The modern periodic table is arranged in order of increasing atomic number.
Mass number and Atomic mass :
  • Mass number is the sum of the number of protons and the number of neutrons present in an atom. It is a whole number.

Mass no. of an atom = No. of protons + No. of neutrons

  • Atomic mass is the average mass of the all of the isotopes of that element. It is a decimal number.
  • For example: Hydrogen has three isotopes – 1H1, 1H2 and 1H3 having mass number 1, 2 and 3 respectively. Naturally occurring hydrogen contains about 99.985% of protium, 0.014% of deuterium and 0.001 % of tritium. Therefore the atomic mass of hydrogen is 1.00784 amu.
  • The atomic mass of an element element is measured in atomic mass unit (amu, also known as Daltons ‘ D’or unified atomic mass unit ‘u’).
  • 1amu = 1.66 x 10-24 grams. 1gm = 6.022 x 1023 amu ( i.e. Avogadro’s number).

Here,

  • Atomic number = Number of protons = Number of electrons = 13
  • Mass number = No. of protons + No. of neutrons
  • No. of neutrons = Mass number – No. of protons = 27-13 = 14.
Atomic mass of first 20 elements
Atomic numberElementAtomic mass
1Hydrogen1.008
2Helium4.0026
3Lithium6.94
4Beryllium9.0122
5Boron10.81
6Carbon12.011
7Nitrogen14.007
8Oxygen15.999
9Fluorine18.998
10Neon20.180
11Sodium22.990
12Magnesium24.305
13Aluminium26.982
14Silicon28.085
15Phosphorus30.974
16Sulfur32.06
17Chlorine35.45
18Argon39.948
19Potassium39.098
20Calcium40.078

Isotopes

Atoms of the same element having same atomic number but different mass number (atomic mass/weight) are called isotopes. For example:

Isotopes of hydrogen :

There are three isotopes of hydrogen:

  1. Protium or ordinary hydrogen
  2. Deuterium or heavy hydrogen
  3. Tritium or radioactive hydrogen.
Name ProtiumDeuteriumTritium
Symbol1H or H2H or D3H or T
No. of protons(P)111
No. of neutrons(n)012
No. of electrons(e)111
Atomic no.(Z)111
Mass no.(A)123

Naturally occurring hydrogen contains about 99.985% of protium, 0.014% of deuterium and 0.001 % of tritium.

Isotopes have different physical properties since they differ in their mass number.

They have same chemical properties since their electronic configuration is same. However, they differ in the rate of chemical reaction. For example, D2 reacts with Cl2 about 13 times slower than H2 does. The different in rate of reaction due to difference in mass of the atoms of the same element is called isotope effect.

Some other examples of isotopic elements :

ElementsIsotopesMost abundant isotope
Carbon6C12, 6C13, 6C146C12
Nitrogen7N14, 7N157N14
Oxygen8O16, 8O17, 8O188O16
Sulphur16S32, 16S33, 16S34, 16S3616S32
Chlorine17Cl35, 17S3717Cl35

Isobars

Atoms of different elements having different atomic number but same mass number are called isobars. For example :

18Ar40, 19K40 and 20Ca40

Isotones

Atoms of different elements having different atomic number and mass number but same number of neutrons are called isotones. For example :

6C14, 7N15 and 8O16

Objective questions and their answers

1. Which of the following is known as heavy hydrogen?

a. Protium c. Tritium

b. Deuterium d. Para hydrogen

2. Which of the following is known as radioactive hydrogen?

a. Protium c. Tritium

b. Deuterium d. Para hydrogen

3. Least abundant isotope of hydrogen is:

a. Protium c. Tritium

b. Deuterium d. Heavy hydrogen

4. Diamond and graphite are :

a. Isotopes c. Isotones

b. Isobars d. Allotropes

5. 6C14 and 8O16 are :

a. Isotopes c. Isotones

b. Isobars d. Allotropes

6. 6C14 and 7N14 are :

a. Isotopes c. Isotones

b. Isobars d. Allotropes

7. All particles residing inside the nucleus of an atom are termed as:

a. Protons c. Electrons

b. Neutrons d. Nucleons

8. What makes the atomic mass fractional ?

a.Prerence of isotopes

b. Number of unpaired electrons

Two Atoms Are Isotopes If They Contain

c. Spherical shape

d. Quantum number.

9. Which of the following are not isotopes:

a. 1H1 and 1H3

b. 18K40 and 20Ca40

c. 6C14 and 7N14

d. Both b and c.

10. Charge present in the nucleus of an atom is :

a. Positive c. Chargeless

b. Negative d. Both +Ve and -Ve

11. Molecular weight of heavy water is :

a. 16 c. 20

Isotopes Are Atoms Of The Same Element With Different Numbers Of Neutrons Which Results In Different

b. 18 d. 22

Answers :

1. b 2. c 3. c

4. d [Note : different forms of same element having different properties are called allotropes]

5. c 6. b 7. d

Google chrome apple. 8. a 9. d 10. a

11. c Note :Heavy waterDeuterium oxide (D2O) is called heavy water. It’s molecular weight is 20 and boiling paint is 101.50C and melting point is 3.80C.

Two Atoms Are Isotopes If

References

Isotopes Are Atoms Of The Same Element With Different Numbers Of Neutrons

  • Sthapit, M.K., Pradhananga, R.R., Foundations of Chemistry, Vol 1 and 2, Fourth edition, Taleju Prakashan, 2005.