Atoms of different elements have the same mass.
According to Dalton’s atomic theory, atoms of different elements have different masses.
Chlorine molecule is a ____.
A molecule of chlorine is made up of two atoms of chlorine, hence it is diatomic.
The number of protons in an atom X, with atomic number Z and mass number A are ____.
The numbers of protons in an atom X of atomic number Z is Z, since, the number of protons is equal to the atomic number (Z) of an atom.
An isotope of ____ is used in the treatment of cancer.
The isotope of cobalt (Co-60) is used in the treatment of cancer.
The maximum number of electrons that can be accommodated in the innermost shell are ____.
The innermost shell in an atom is K-shell and it can accommodate a maximum of 2 electrons.
Which is the incomplete shell in Li atom?
The electronic configuration of Li is 2,1(K,L). Hence, L-shell of lithium atom is incomplete.
Which of the following is the first step to write an equation?
Equations contain both symbols and formulae. Therefore, to write an equation, first the statement should be changed to symbols and formulae.
Which of the following atoms do not have neutrons?
Hydrogen atom has no neutrons. It has 1 electron and 1 proton.
Which of the following element forms a triatomic molecule?
Ozone is a triatomic molecule of oxygen. In one molecule of ozone, there are three oxygen atoms.
The number of electrons in an atom is 8 and the number of protons is 7. Then the charge on an atom will be ____.
As the number of protons is one less than the number of electrons, the charge will be −1.
If a neutral atom has two shells completely filled up, then atomic number of the atom is ____.
A neutral atom with first two shells complete is 10. K + L = 2 + 8 = 10 The atomic number of the atom is 10.
The symbol △ in a chemical equation indicates ____.
The symbol △ in a chemical equation indicates heat.
One observation that helps us to say a chemical reaction has taken place is change of temperature.
Heat may be evolved or absorbed during a reaction. So, a chemical reaction can be identified by the change of temperature.
What is the valency of phosphate ion?
Phosphate is a trivalent ion. Therefore, its valency is 3.
The number of electrons in the last shell of krypton are ____.
Krypton has 8 electrons in its last shell.
The symbol of chromium is ____.
The symbol of chromium is Cr.
A molecule is made up of atoms.
A molecule is formed by the chemical combination of two or more atoms of same or different elements.
The subscript (s) mentioned after a symbol or formula of a substance, in a chemical equation indicates ____.
The subscript (s) mentioned after a symbol or formula of a substance, in a chemical equation indicates that the physical state of that substance is solid.
The number of valence electrons in neon atom are ____.
In neon atom there are 8 valence electrons.
The electronic configuration of an element with atomic number 12 is ____.
The electronic configuration of an element with atomic number 12 is 2,8,2.
The electronic configuration of oxygen atom is ____.
The atomic number of oxygen is 8. Therefore, the electronic configuration of oxygen atom is 2,6.
A chemical equation is represented by using only formulae.
A chemical equation is represented by using both symbols and formulae.
Atomicity of sulphur is ____.
Atomicity of sulphur is 8. Therefore, sulphur is octa atomic.
The symbol (↓) mentioned next to a substance in a chemical equation indicates ____.
The symbol (↓) in a reaction indicates that a precipitate is formed.
Modern atomic symbols are based on the method proposed by ____.
A Swedish chemist Berzelius introduced the first universally acceptable system of atomic symbols.
The number of atoms present in a molecule of an element is called ____.
Atomicity is defined as the number of atoms present in one molecule of an element.
The N-shell can accommodate a maximum of 32 electrons.The N-shell can accommodate a maximum of 32 electrons.
The maximum number of electrons that can be accommodated in the N-shell (fourth shell) are 32.
The compounds are formed by combination of atoms. This law was stated by ____
According to Dalton's atomic theory, the compounds are formed by the combination of atoms.
The indivisibility of atom was proposed by ____.
According to Dalton’s atomic theory, an atom cannot be created, divided, or destroyed as a result of a chemical change.
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