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Indian Navy SSR (Sailor) Atoms and Elements — practice questions

Explore 31 free Atoms and Elements questions in Indian Navy SSR (Sailor) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Atoms and Elements questions and exercises with answers

Showing questions 1–30 of 31.

For a hydrogen-like atom of nuclear charge $Z$, the radius of the $n$th Bohr orbit scales asRead the answer and worked solution →An electron is accelerated through a potential difference of $100\,V$. Its de Broglie wavelength is approximatelyRead the answer and worked solution →As per your syllabus, what is the MOLECULAR MASS of methane (CH₄) — using C = 12.011 u and H = 1.008 u?Read the answer and worked solution →As per your syllabus, the charge-to-mass ratio e/m_e of the electron, measured by J.J. Thomson in 1897, is which value?Read the answer and worked solution →The de Broglie wavelength of a particle with momentum p is:Read the answer and worked solution →Order the atomic models as they were proposedRead the answer and worked solution →Match each scientist to their modelRead the answer and worked solution →Match each model to what it could NOT explainRead the answer and worked solution →True or false: Rutherford's modelRead the answer and worked solution →True or false: Bohr's modelRead the answer and worked solution →Complete the reason Bohr's model failsRead the answer and worked solution →Which model does this belong to?Read the answer and worked solution →Match each quantum number to what it is calledRead the answer and worked solution →True or false: the quantum mechanical modelRead the answer and worked solution →Order the structure: from atom down to electronRead the answer and worked solution →Complete the (n + l) ruleRead the answer and worked solution →True or false: orbital energiesRead the answer and worked solution →Match each rule to what it forbids or requiresRead the answer and worked solution →Tap every statement Hund's rule requiresRead the answer and worked solution →The fundamental particlesRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Which principle is being described?Read the answer and worked solution →Flip and pair: symbol with meaningRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Tap every statement true of the Schrodinger modelRead the answer and worked solution →Reading the models backRead the answer and worked solution →Assertion and reason: filling orbitalsRead the answer and worked solution →True or false: shells and subshellsRead the answer and worked solution →

Worked practice questions

For a hydrogen-like atom of nuclear charge $Z$, the radius of the $n$th Bohr orbit scales as

  1. $r_n \propto nZ$
  2. $r_n \propto n^2/Z$
  3. $r_n \propto Z/n^2$
  4. $r_n \propto n/Z^2$
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Correct answer: B. $r_n \propto n^2/Z$

$r_n = (0.529\,Å)\,n^2/Z$. **So radius grows as $n^2$ but shrinks as $Z$ — explaining why He$^+$ has a smaller $n=1$ orbit than H.**

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An electron is accelerated through a potential difference of $100\,V$. Its de Broglie wavelength is approximately

  1. $1.23\,Å$
  2. $12.3\,Å$
  3. $0.0123\,Å$
  4. $0.123\,Å$
Show answer and solution

Correct answer: A. $1.23\,Å$

For an electron accelerated through $V$ volts, $\lambda = \dfrac{12.27}{\sqrt{V}}\,Å$. With $V = 100$: $\lambda = 12.27/10 \approx 1.23\,Å$. This is comparable to atomic spacings — basis of electron diffraction.

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As per your syllabus, what is the MOLECULAR MASS of methane (CH₄) — using C = 12.011 u and H = 1.008 u?

  1. 17 u
  2. 20 u
  3. 16.043 u (= 12.011 + 4 × 1.008)
  4. 12 u
Show answer and solution

Correct answer: C. 16.043 u (= 12.011 + 4 × 1.008)

As per your syllabus, example, CH₄ molecular mass = 12.011 + 4(1.008) = 16.043 u.

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More Chemistry topics

Chemical EquilibriumOrganic ChemistryThe p-Block ElementsAlcohols Phenols EthersAtoms and MoleculesClassification of Elementsp-Block ElementsPolymers