MCQ
In Rutherford’s experiment, most α-particles passed straight through the gold foil. What does this observation most strongly suggest?
A. The nucleus occupies most of the atom
B. Electrons have a positive charge
C. Most of the volume of an atom is empty space
D. Positive and negative charges are uniformly distributed
C. Most of the volume of an atom is empty space
Assertion (A): The idea of indivisible particles of matter was proposed in ancient India as well as ancient Greece.
Reason (R): Acharya Kanada called these particles Parmanus, while Leucippus and Democritus used the term Atomos.
A. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
I am a neutral particle located inside the nucleus. My mass is nearly equal to that of a proton, but I have no charge. I was discovered by James Chadwick in 1932.
Who am I?
NEUTRON
J.J. Th_ms_n c_nd_ct_d an _xp_r_m_nt using c_th_de r_ys in a v_c__m t_be. He f__nd that c_th_de r_ys w_re str__ms of n_g_t_v_ly ch_rged p_rt_c_es c_lled _l_ct_ons. He th_r_f_re c_ncl_d_d that _l_ct_ons w_re pr_s_nt ins_de the _t_m.
J.J. Thomson conducted an experiment using cathode rays in a vacuum tube. He found that cathode rays were streams of negatively charged particles called electrons. He therefore concluded that electrons were present inside the atom.
I sit at the centre, dense and small,
Positive charge is part of me, that is all.
Most of the atom is not where I stay,
Yet almost all its mass is found my way.
Who am I?
NUCLEUS
An atom has 8 protons, 8 neutrons and 8 electrons. Another atom has 8 protons, 10 neutrons and 8 electrons. Which statement correctly compares them?
A. They are isobars because their mass numbers are different
B. They are isotopes because they have the same atomic number but different mass numbers
C. They are different elements because their neutron numbers differ
D. They have different chemical properties because their mass numbers differ
B. They are isotopes because they have the same atomic number but different mass numbers
Assertion (A): J.J. Thomson concluded that cathode rays were made of negatively charged particles.
Reason (R): The rays travelled from the negatively charged cathode towards the positively charged anode in a vacuum tube.
B. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
I am an atomic model in which electrons are allowed to occupy only specific energy levels. I explain why electrons can remain in these allowed orbits without continuously radiating energy.
Who am I?
BOHRS ATOMIC MODEL
R_th_rf_rd’s g_ld f__l _xp_r_m_nt sh_wed that m_st _lp_a p_rt_c_es p_ssed str__ght thr__gh the f__l. A sm_ll fr_ct_on w_re d_fl_cted, sh_w_ng a t_ny d_nse n_cl_us.
Rutherford’s gold foil experiment showed that most alpha particles passed straight through the foil. A small fraction were deflected, showing a tiny dense nucleus.
I am found by counting the particles in the nucleus,
Protons and neutrons together give me my value.
I tell you the total number of nucleons in an atom.
Who am I?
MASS NUMBER
An electron in a Bohr orbit moves around the nucleus without continuously losing energy. Which postulate directly explains this?
A. Electrons are embedded in a sphere of positive charge
B. Electrons can occupy only specific stationary energy levels
C. Electrons and protons have equal masses
D. The nucleus contains only neutrons
B. Electrons can occupy only specific stationary energy levels
Assertion (A): The discovery of the neutron helped account for the mass present in the nucleus in addition to that due to protons.
Reason (R): Neutrons have a mass nearly equal to that of protons and are located inside the nucleus.
A. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
I am found inside the nucleus. I carry a positive charge of +1 and have a relative mass of approximately 1 u. I was discovered/named by Rutherford.
Who am I?
Acc_rd_ng to B__r’s m_d_l, _l_ct_ons c_n _cc_py only c_rt_in d_scr_te _n_rgy l_v_ls. Wh_le r_m__n_ng in an _ll_wed l_v_l, an _l_ct_on d_es not r_d__te _n_rgy.
According to Bohr’s model, electrons can occupy only certain discrete energy levels. While remaining in an allowed level, an electron does not radiate energy.
I do not hide deep inside the atom,
I stay in the shell farthest from the nucleus.
My number helps decide how an atom combines with others.
Who am I?
VALANCE ELECTRONS
An atom is represented as ²³₁₁Na. A student claims that it contains 23 protons and 11 neutrons. What is the correct evaluation of the student's claim?
A. Correct, because the upper number represents protons
B. Correct, because the lower number represents neutrons
C. Incorrect; it contains 11 protons and 12 neutrons
D. Incorrect; it contains 23 protons and 11 electrons
C. Incorrect; it contains 11 protons and 12 neutrons
Assertion (A): John Dalton proposed the first scientific atomic theory in 1808.
Reason (R): Dalton's atomic theory stated that electrons are embedded in a positively charged sphere.
C. Assertion is true, but Reason is false.
I am a pair of atoms. We have different identities because our numbers of protons are different, yet we share the same total number of nucleons. Because of this similarity, our mass numbers are identical, but our chemical properties are different.
ISOBARS
_s_t_p_s h_ve the s_me _t_m_c n_mb_r but d_ff_r_nt m_ss n_mb_rs. _s_b_rs h_ve the s_me m_ss n_mb_r but d_ff_r_nt _t_m_c n_mb_rs.
Isotopes have the same atomic number but different mass numbers. Isobars have the same mass number but different atomic numbers.
I am not identified by my name but by a number,
My place in the atom is revealed when n=3n=3.
My maximum capacity is greater than that of the shell before me,
Yet I may remain only partly filled while another shell begins to fill.
Who am I?
M SHELL
Consider an atom with electronic configuration 2,8,7. Which prediction is most consistent with the rules given in the chapter?
A. Its valency is 7 because it has seven valence electrons
B. Its valency is 1 because it requires one electron to achieve a stable octet
C. Its valency is 8 because the outer shell can hold eight electrons
D. Its valency is 0 because the first two shells are completely filled
B. Its valency is 1 because it requires one electron to achieve a stable octet
Assertion (A): Every atom contains at least one neutron in its nucleus.
Reason (R): A neutron is a neutral subatomic particle with a relative mass nearly equal to that of a proton.
D. Assertion is false, but Reason is true.
I am not a particle, yet I determine the identity of an element. I represent the total number of positively charged particles in the nucleus. In a neutral atom, my numerical value is also equal to the number of electrons.
Who am I?
ATOMIC NUMBER
An _t_m has 2,8,7 l_ct_ons in its sh_lls. To become st_bl, it can g__n one _l_ct_on rather than l_s_ng seven, because its _ut_rm_st sh_ll then contains a c_mpl_te _ct_t.
An atom has 2,8,7 electrons in its shells. To become stable, it can gain one electron rather than losing seven, because its outermost shell then contains a complete octet.
I carry a positive charge, yet I am not a proton alone.
I was fired towards a thin sheet of gold to reveal secrets hidden inside the atom.
Most of my kind passed straight through, some changed direction, and a very few returned almost to where they began.
Who am I?