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Write a scientific reason.
Boron and oxygen elements are placed in the second period in periodic table.
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Write a scientific reason.
In group 2, beryllium and calcium elements, calcium is more electropositive element than beryllium.
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Complete the following chart.
| Shell | n | 2n2 | Electron holding capacity |
| K | 2 × 12 | 2 | |
| L | 2 | 8 | |
| 3 | 2 × 32 | 18 | |
| N | 4 | 2 × 42 |
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Find the period in which these elements can be placed.
4Be, 17Cl, 2He, 13Al
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Electronic configuration of element A is 2,8,1. Answer the following questions based on this information.
- What is the atomic number of element A?
- Find the group to which this element belongs.
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What is an electric motor?
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In which electric motor appliances do we use it?
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Distinguish between:
Group - Period
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Write a short note.
Moon missions
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Write name of elements, symbol, atomic number, electronic configuration of second period in modern periodic table?
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Identify periods of elements and blocks of elements from given electronic configuration.
- 2, 8, 2
- 2, 8, 7
- 2, 1
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Observe the given chart and answer the questions given below.
| Element | A | B | C | D |
| Electronic configuration | 2, 1 | 2, 8 | 2, 8, 1 | 2, 8, 8 |
- Which elements are in the same row?
- Which elements have the same column?
- Which elements are in the 18th column?
- Which element is more reactive among A and C?
- Which of the following elements A or B will form compounds?
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XY compound is formed by X (Atomic number 11) and Y (Atomic number 17), then answer the questions given below.
- Determine the position of the element X and Y periodic table.
- Which type of elements X and Y are metals, nonmetals or metalloids?
- From which block the elements X and Y are?
- Determine the electronic configuration and valency of these elements.
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Observe the periodic table given below and write the answers of the questions.

- Write the name and valencies of the elements in 3rd row.
- Classify the elements in this row as metal, nonmetal and metalloids.
- Which block does nonmetals belong to?
- Write name of any two metalloid elements.
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Make a chart which shows the name of the element, valency, atomic number, electronic configuration in the 2nd row of the modern periodic table and arrange these elements in ascending order of atomic mass.
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Observe the figure and write the answers to the questions asked.

- The construction shown in the figure is of which device?
- Explain the principle on which this device works.
- Write any three uses of this device.
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In a double displacement reaction ______.
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Observe the following diagram and answer the questions.

- Construction of which equipment does the above diagram show?
- On which principle does this equipment work?
- According to which law the coil ABCD rotates?
- Write the law in your own words.
- Where is this equipment used?
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Add potassium chromate (K2CrO4) into the solution of barium sulphate (BaSO4).
- What was the colour of the precipitate formed? Also, write the name of the precipitate.
- Write down the balanced equation for this reaction.
- Will you call this reaction a displacement reaction or a double displacement reaction? Why?
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What is the electronic configuration of K19?
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