Question

Learning Goal: This question reviews the format for writing an element's written symbol. Recall that written symbols have a particular format. Written symbols use a form like this: 17 In this form the mass number, 35, is a stacked superscript. The atomic number, 17, is a stacked subscript. Cl" is the chemical symbol for the element chlorine. A general way to show this form is: mass number It is also correct to write symbols by leaving off the atomic number, as in the following form 35Cl or mas number Symbol This is because if you write the element symbol, such as CL you know the atomic number is 17 from that symbol. Remember that the atomic number, or number of protons in the nucleus, is what defines the element Thus, if 17 protons are in the nucleus, the element can only be chlorine. Sometimes you will only see 35Cl where the atomic number is not written. Watch this video to review the format for written symbols. In the following table each column represents a neutral atom. Fill in the gaps in the following table by working this problem out on a separate sheet of paper. You will need the periodic table in the 'resources" drop down menu in the upper right hand corner of this question to look up atomic numbers and masses. Symbol 52Cr Protons Neutrons Electrons Mass no. 26 82 30 64 48 86 222 207 Use the hints in the following part whenever needed to review the steps to filling in this type of table.

Answer 1

C^52_r Rightarrow c_r Rightarrow chromium atomic number 24 protons Rightarrow 24, Neutrons = mass number - proton no. electrons Rightarrow 24, Mass no.: 52 2) protons Rightarrow 26 Rightarrow atomic no. 26 Rightarrow Iron Fe. F^56_e neutrons = 30 electrons = 26, Mass no = proton + neutron = 30 + 26 = 56 3) electrons Rightarrow 48, atomic = 48 Rightarrow cd protons = 48 neutrons Rightarrow 64 mass no: 64 + 48 = 112 cd^112 5) protons = 82, atomic number 82 Rightarrow pb Rightarrow lead mass no. 207 no. of electrons = 82 neutrons = 207 - 82 = 125 pb^207 4) electrons 56, protons = 86 Rightarrow Radon Rn mass number 222 numbers = 222 - 86 = 136 Rn^222
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