NJC 3 Atomic Structure Checkpoint

National Junior College SH1 H2 Chemistry 1 Checkpoint 1 1 State the number of protons, electrons and neutrons for the following particles: Particles Nucleon number No. of protons No. of neutrons No. of electrons P31 15 31 15 16 15 +240 20Ca 40 20 20 18 −232 16 S 32 16 16 18 Generally, except for 𝑯𝟏 𝟏 , number of neutrons  number of protons for other elements. 2 Which of the ions has more electrons than protons and more protons than neutrons? [Given: H]DO,H,He, 2 1 16 8 1 1 4 2 = A He+ B OH− C D3O+ D OD− Nucleon number No. of protons No. of neutrons No. of electrons He+ 4 2 2 1 OH− 17 9 8 10 D3O+ 22 11 11 10 OD− 18 9 9 10 3 Oxygen has two isotopes, 16O and 18O. An oxide ion, −yxO8 has the same number of neutrons and electrons. What could be the values of x and y? x y A 16 1 B 16 2 C 18 1 D 18 2 x y No. of neutrons No. of electrons A 16 1 8 9 B 16 2 8 10 C 18 1 10 9 D 18 2 10 10

National Junior College SH1 H2 Chemistry 2 4 In 1999 Russian chemists claimed to be the first to identify atoms of a new element of proton number 114. This was produced by bombarding atoms of plutonium, Pu, with the atoms of an isotope of a group 2 element, X. The reaction taking place is as shown below. 𝑃𝑢 + 𝑿 → [𝑛𝑒𝑤 𝑒𝑙𝑒𝑚𝑒𝑛𝑡] + 3 𝑛𝑒𝑢𝑡𝑟𝑜𝑛𝑠 ( 𝑛0 1 )𝟏𝟏𝟒 𝟐𝟖𝟗 94 244 What is X? A Mg B Ca C Sr D Ba [N03/1/4] Nucleon number and charge are always conserved. Proton number is also conserved since electrons are not involved in this nuclear reaction. To identify X, determine its proton number. proton number of 114 – 94 = 20.  X is Ca.

National Junior College SH1 H2 Chemistry 3 Checkpoint 2 The angle of deflection, θ, is proportional to the charge mass of the particles. The charge mass ratio of the O2– ion is the highest amongst the four. Hence O2– will deflect the most 2 When passed through an electric field, the 1H nucleus is deflected as shown below. [Note: 1H nucleus refers to 1H+ (all electrons removed)] Which of the above beams represents the deflection for an ion 2X2–? θ = k × charge mass for 1H+, +4 = k × +1 1 , k = 4 for 2X2–, angle of deflection for 2X2– = 4 × ( −2 2 ) = – 4o 3 A plasma is a gaseous mixture in which atoms have been completely stripped of their electrons, leaving bare nuclei. When passed through an electric field, the 1H nucleus is deflected at an angle of +4 . What will be the angle of deflection for the 3H nucleus in the same plasma? A +0.75 B +1.3o C +4o D +12o Angle of deflection = k × charge mass For the 1H nucleus, +4 = k ×( +1 1 ). Hence k = 4. For the 3H nucleus, angle = 4 × ( +1 3 )= +1.3 1 Use of the Data Booklet is relevant to this question. Which of the ions will be deflected the most in a