Question

B) Theories must be testable; hypotheses do not need to be testable. CHypotheses are educated guesses, and theories are tentative explanations. D) Hypotheses are derived from experimentation, whereas theories are derived from observation. 12) A) Water is an example of an element. B Nitrogen C) Glucose D) Salt 13) What are the four most common elements found in living organisms? A) nitrogen, oxygen, phosphorus, and carbon carbon, oxygen, nitrogen, and hydrogen C) carbon, oxygen, potassium, and calcium D) oxygen, calcium, hydrogen, and carbon 14) Which of the following elements is a trace element that is essential to life? phosphorus B) carbon C) iron D) calcium 15) In order to have a positive charge, an atom must have _ A) more protons than electrons B) more electrons than protons C) more neutrons than protons D) more protons than neutrons 16) All atoms of an element have the same number of A) protons plus neutrons B) protons electrons D) neutrons 17) An atom's are found in its nucleus. ) neutrons and protons B) protons only D) electrons, protons, and neutrons C) neutrons and electrons 18) Beryllium's atomic mass is 9, and its atomic number is 4. How many protons are found in a beryllium atom? A) 9 B) 13 C)4 DS 19) An uncharged atom of mercury has an atomic number of 80 and an atomic mass of 200. This atom has protons, _neutrons, and electrons. A) 80; 120: 80 B) 120; 80: 120 C) 120; 280; 120 D) 80; 40; 80 20) The way Earth moves about the sun is most like A) a neutron and electron moving around a proton ® an electron moving around the nucleus of an atom C) a proton moving about an electron D) a neutron moving about a proton 21) Isotopes of an element have the same number of and different numbers of protons, neutrons D) electrons, protons B) protons, electrons C) neutrons, protons 22) How do radioactive isotopes differ from isotopes? A) Radioactive isotopes have more neutrons than do isotones. B) Radioactive isotopes are stable; isotopes are unstable.

Answer 1

Answer 12 (B) because Nitrogen (N), non-metallic element of the periodic table in group 15[ Va]. It is a colourless, odorless, tasteless gas which is the most abundant element in the atmosphere of Earth and is a constituent of all living matter.

Answer 13 (B) because Approximately 96 percent of the human body's mass consists of just four elements: oxygen, carbon, hydrogen, and nitrogen, with all of that in the form of water.

Answer 14 (C) Iron as a component of hemoglobin and myoglobin also plays a crucial role in oxygen transport.

Answer 15 (A) because The atom may obtain a positive charge or a negative charge, depending on whether the number of electrons in an atom is greater or less than the number of protons in that atom.

Answer 16 (C) because In a given atom the number of electrons is equal to the number of protons in that atom. Units of the same product can however have different electrons numbers. Such units are called ions. Atoms which lose one or more electrons are charged positively, and are called cations.

Answer 17 (A) because Electrons are the smallest of the three particles which constitute atoms. Electrons are found in shells or orbitals which surround an atom's nucleus. The nucleus comprises the protons and neutrons. They are grouping together in the atom centre.

Answer 18 (D) because Beryllium is used as an alloy agent for the manufacture of beryllium copper, which is commonly used for springs, electrical contacts, spot-welding electrodes and non-saving devices.

Answer 19 (A) because Number of Protons: Thus, as the number of protons found in the nucleus is equal to the atomic number. Consequently, as given, the atomic number is 80, Hg contains 80 protons respectively.

Number of electrons: Hg holds no form of charge, as indicated in the sentence. This means, in fact, the atom is neutral. That means, to give a neutral atom, this carries the same number of electrons that the number of protons does. Consequently it contains 80 electrons.

Neutron Number: The number of neutrons can be calculated with the following formula,Neutron No.= Atomic Mass-Proton Number Thus, Atomic Mass= 200 So, Neutron Number= 200-80= 120 Neutron No.

Answer 20. (B) an electron moving around the nucleus of an atom because The atom's Bohr model— or model of the solar system — describes atoms as consisting of a nucleus with a number of electrons in orbits around that nucleus, similar to a solar system. Because of this, humans have hypothesized that atoms might be like tiny solar systems.

Answer 21. (A) because Atoms of the same compound are classified as isotopes, having the same number of protons but different number of neutrons. Isotopes of any given element all contain the same number of protons, so they have the same number of atoms (for example, the helium atomic number is always 2).

Answer 22. (A) Radioisotopes are elementary radioactive isotopes. They can also be defined as atoms containing an unstable neutron and proton combination, or excess energy in their nucleus.