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An element has atomic number 13 and an atomic mass of 27.
(a) How many electrons are there in each atom of the element ?
(b) How are these electrons distributed in the various energy levels ?
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Write the distribution of electrons in an atom of element whose atomic number is 18. What is special about the outermost electron shell (or valence shell) of the atom of this element?
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Which of the following is the correct electronic configuration of sodium?
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Which of the following represents the correct electron distribution in magnesium ion?
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The correct electronic configuration of a chloride ion is :
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From the Symbol `""_15^31"P"`, State : Electron Configuration of Phosphorus.
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The atom of an element X has 7 electrons in its M shell.
(a) Write the electronic configuration of element X.
(b) What is the atomic number of element X?
(c) Is it a metal or a non-metal?
(d) What type of ion will be formed by an atom of element X? Write the symbol of the ion formed.
(e) What could element X be?
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Magnesium and oxygen combine in the ratio of 3 : 2 by mass to form magnesium oxide. What mass of oxygen gas would be required to react completely with 24 g of magnesium ?
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A liquid compound X of molecular mass 18 u can be obtained from a number of natural sources. All the animals and plants need liquid X for their survival. When an electric current is passed through 200 grams of pure liquid X under suitable conditions, then 178 grams of gas Y and 22 grams of gas Z are produced. Gas Y is produced at the positive electrode whereas gas Z is obtained at the negative electrode. Moreover, gas Y supports combustion whereas gas Z burns itself causing explosions.
- Name (i) liquid X (ii) gas Y, and (iii) gas Z.
- What is the ratio of the mass of element Z to the mass of element Y in the liquid X ?
- Which law of chemical combination is illustrated by this example ?
- Name two sources of liquid X.
- State an important use of Y in our life.
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Define ‘formula mass’ of a compound.
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State whether the following statements are true or false:
A sodium ion has positive charge because it has more protons than a neutral atom.
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State whether the following statements are true or false :
A chloride ion has negative charge because it has more electrons than a neutral atom.
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What is the name of a particle which contains 10 electrons, 11 protons and 12 neutrons ?
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Name the particle which has 18 electrons, 18 neutrons and 17 protons in it.
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Fill in the following blank with suitable word :
The particle which is formed by the gain of electrons by an atom is called ..............
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Fill in the following blank with suitable word:
The particle which is formed by the loss of electrons by an atom is called..............
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Fill in the following blank with suitable word:
The particle which is formed by the loss or gain of electrons by an atom is called..............
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Fill in the following blank with suitable word:
A potassium ion has positive charge because it contains less............... than.....................
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Fill in the following blank with suitable word:
A sulphide ion has negative charge because it contains less ....................... than ...................
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An element X has a valency of 2. Write the simplest formula for bromide of the element.
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