Tag: chemistry

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Multiple choice chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

Predict the formulae of the binary compounds formed by combination of the following pairs of elements:
(i)    Magnesium and nitrogen
(ii)   Silicon and oxygen

  1. $MgN _{2}, SiO _{2}$
  2. $Mg _{3}N _{2}, SiO _{2}$
  3. $Mg _{2}N _{3}, Si _{2}O _{3}$
  4. $MgN, SiO _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Three Mg ( $+2$ oxidation state) combine with two N ($-3$ oxidation state) to form $Mg _3N _2$.

One Si ( $+4$ oxidation state) combine with two O ($-2$ oxidation state) to form $SiO _2$.

Note: In a neutral molecule, the total charge on cations is numerically equal to the total charge on anions.

Multiple choice chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

Predict the formula of stable compound formed by an element with atomic number 114 and fluorine.

  1. $AF _{3}$
  2. $AF _{2}$
  3. $AF$
  4. $AF _{4}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Element A with atomic number 114 will share four electrons to attain stable noble gas electronic configuration. It falls in the Carbon family.

Fluorine shares one electron to attain stable noble gas electronic configuration. One atom of A combines with four atoms of F to form $AF _4$.

Hence, the correct option is $\text{D}$
Multiple choice chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

Law of octaves stated :

  1. every eighth element had properties similar to the first element

  2. every third element had properties similar to the first element

  3. the properties of the middle element were in between the other two members

  4. the properties of the elements were repeated after regular intervals of 3,4 or 8 elements
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Newland's Law of octaves stated that if elements (known at Newland's time) were arranged in increasing order of their atomic weights, every eighth element had properties similar to the first element. For example, Li and Na have similar properties.

Multiple choice chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

What were the limitations of Newlands' classification?

  1. It was applicable only for lighter elements

  2. He adjusted two elements on the same place

  3. The pattern was only observed up to calcium

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The limitations of Newlands' classification were:

  • It was only applicable for lighter elements.
  • He adjusted two elements in one place.
  • The pattern was only observed up to calcium.

Multiple choice chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

The placement of elements in the Newlands' table was compared to :

  1. weeks of a month

  2. notes of music

  3. months of a year

  4. days of a month
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The placement of elements in the Newlands' periodic table was compared to the notes of music where the first note and the eighth note are same. Similarly, in Newlands' periodic table, the chemical properties also repeat after $7$ elements.

Multiple choice chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

If X and Y are two elements which belong to same group of Newland's periodic table, how many elements exists between X and Y?

  1. $4$
  2. $5$
  3. $6$
  4. $7$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Newland's periodic table, $1$st element and the $8$th element have the same chemical property, i.e., they belong to the same group. So, the table will look like:
$\begin{equation}X\;1\;2\;3\;4\;5\;6 \ Y\end{equation}$
So, there are $6$ elements between X and Y.