What element has an electron arrangement of 3, 8, 8, 2? a. Chlorine B. Calcium c

Question

What element has an electron arrangement of 3, 8, 8, 2? a. Chlorine B. Calcium c. Carbon d. Fluorine e. Manganese How many milligrams of a 1.0 g sample of strontium-85 will remain active after 195 days, given that it has a half-life of 65 days? Use 2 significant figures a. 160 b. 250 c. 400 d. 130 e. 0.13 Identify the type of particle or radiation for. a. Alpha b. Positron c. Beta d. Neutron e. None of the Above What is the molarity of NaOH if 25.00 ml of an aqueous 6.000 M HCI solution is titrated with 47.00 ml of the unknown NaOH solution? a. 11.28 M b. 0.1128 M c. 0.250 M d. 3.191 M e. 0.391 M

Explanation / Answer

64. Answer:- B

Electronic arrangement:-2,8,8,2

Atomic number:-20

So the element is calcium.

65. Answer:-

Half life is 65 days so 195 days involve 3 half life. After each half life activity is reduced to 1/2 so after 3 half life activity would reduce to 1/8.

1g sample would reduce to (1/8)g i.e 125mg.

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.