Question

21. Which general statement does NOT apply to metals? (1 point)

Answer 1

Answer:

21. Most metals are brittle

22. Increases from top to bottom within the group.

23. Neon is the most stable element because its highest occupied energy level is filled.

24. transfer of electrons.

25. electrons are not shared equally between atoms.

26. BeCl2

27. double-replacement and decomposition

28. exothermic

29. The reaction rate decreases.

30. The salt dissolved most quickly in the warm water

31. Saturated

32. feels slippery

33. hydroxide ions in solution.

34. stay about the same.

35. Change into a different element altogether

36. an alpha particle

37. nuclear change.

38. Tremendous amount of mass

39. 1 km/1000 m

40. each element contributes an equal number of atoms

41. a bee hovering around a bee hive

42. the number of valence electrons in atoms of the element.

Explanation:

21. Metals are malleable , ductile and good conductor of electricity. But most metals are not brittle . Most don't break easily when deformed.

22. As the atom size increase moving from top to bottom in alkali metals  the energy required to lose electron drops rapidly. The outer electron becomes further from the nucleus as we move down the group and this increase reactivity down the group. Reactivity increases as we move from top to bottom in alkali metals.

23. Neon is the most stable elements among the list because it has fulfilled the octet rule . The shell is completely filled.  It can be written as 2 8.

24. Ionic bonding involves transfer of electron(s). One atom lose electron while the other atom receive electron.

25. Polar covalent bonds, the pairs of atom are unequally shared between atoms. This happens between atoms of different electronegativities. example HCl.

26. Beryllium has a charge of +2 and chlorine is -1 . Combining the charge

Be2+ and Cl-

cross multiply the charge

BeCl2

27. Double replacement takes place between the reaction of magnesium carbonate and nitric acid because Mg replace hydrogen in the compound(HNO3) and H replace Mg in the compound(MgCO2). The other reaction is decomposition reaction because a single compound(Carbonic acid) split to form two compound.

28. 2Cu + O2  → 2CuO  + 315 kJ . The reaction above is an exothermic reaction as heat and energy is released to the environment. The enthalpy change is the difference between the energy of the reactant and product. Since the energy is positive, it simply infer that energy is release to the surrounding.

29. The reaction rate will decrease if oxygen is decreased. The reaction will take time before completion because of lack of oxygen. Normally oxygen increases burning.

30. The salt will dissolve more quickly in warm water because the molecules in warm water moves rapidly therefore breaking bonds in other substance faster.

31.  A Saturated solution is a solution that contain more solute than the solvent can hold at that temperature.

32.  Acid usually taste sour , reacts with metals to form the corresponding salt and also changes the color of indicator. But acid are not slippery.

33. A base is a substance that produces hydroxide ion in aqueous solution.

34. Buffer solution is a solution that resist change in pH on addition of small acid or base.

35. Uranium -238 undergoes alpha decay to produce a different element. The decay can be represented as

238 U → 234 Th + 4  2He. The 4 is superscript and 2 is subscript. Thorium is formed in this alpha decay.

36. An alpha decay occurred . 212Po → 208Pb + 4 2He. Mass number decrease by 4 and atomic mass decrease by 2.

37. Transmutation is a change from one chemical element to another. The change occurs in the nucleus of an atom. The change is therefore a nuclear reaction.

38. Nuclear fission is the disintegration of large atomic nucleus into smaller nuclei.

39.  1 kilometers  = 1000 meters

       18 kilometers = 18 × 1000 meters = 18000 meters.

40. Dalton's law of combination described that atom of elements combines in 1:1 to form a compound.

41. Electron revolves around the shell of an atom. The best analogy is bee hovering around  a  bee hive.

42.   The valency electron of an atom determines how an atom reacts. For example single valency electron react very rapidly.

Answer 2

Answer:

21. Most metals are brittle.

22. increases from top to bottom within the group

23. Neon is the most stable element because its highest occupied energy level is filled.

24. transfer of electrons

25. electrons are not shared equally between atoms

26. BeCl2

27. double-replacement and decomposition

28. exothermic

29. The reaction rate decreases.

30. The salt dissolved most quickly in the warm water.

31. saturated

32. feels slippery

33. hydroxide ions in solution

34. stay about the same

35-40. I do not know.

41. a bee hovering around a bee hive

42. the number of valence electrons in atoms of the element

Explanation:

21. Metals are ductile and malleable (conveniently also characteristics for chewing gum). They are stretchy and squishy. Brittle is the opposite of stretchy and squishy, and is a characteristic of non-metals.

22. On the periodic table, elements higher up are safer to use in labs. They are safer because they are less likely to react with other substances. Therefore the tendency to react with other substances increases from top to bottom within the group.

23. "Noble gases stable" (periodic table song by ASAP Science). Neon is a noble gas, therefore it is stable. When elements have only one electron to gain or lose, they are very reactive or least stable.

24. The formation of an ionic bond (metal + non-metal) is caused by the giving and receiving of electrons. Neutrons and protons do not transfer. Electrons are shared in covalent/molecular bonds (between non-metals).

25. A polar covalent bond occurs between non-metals, therefore they share electrons (ionic bonds transfer electrons). Non-metals become anions (whereas metals become cations). Polar bonds have unequal sharing and nonpolar bonds have equal sharing.

26. A one-to-two ratio of  beryllium ions to chloride ions means for every Be, there are two Cl. The number of atoms is represented by the ratio, and the numbers of atoms are written as subscripts after the element symbol.

27. MgCO2  reacting with HNO3  to form magnesium nitrate and carbonic acid is a double-replacement reaction. The elements in the beginning substances "switch partners" to form the products.

Carbonic acid then breaks down into water and carbon dioxide is decomposition. This occurs when the elements that make up a compound are split up.

28. In 2Cu + O2  => 2CuO + 315 kJ , the energy is on the right side. The right side is the products, or the stuff that was made. kJ is a unit to measure energy, therefore energy was made. Exothermic is the term that means energy was released.

29. Since oxygen is needed for a fire to burn, decreasing the oxygen slows the reaction rate (the reaction is burning, formally known as combustion).

30. Two things help substances dissolve: heat and stirring. Warm water is hotter than room-temperature water and ice water. This makes the salt dissolve faster.

31. A solution that contains more solute than it would normally hold is saturated. Saturated means there is a more than concentrated amount of solute in the solution. Concentrated is when there is a maximum amount of solute that will dissolve.

32. Acids do not feel slippery -- that is a characteristic of a base. To remember, bases are generally soaps and soaps are slippery. Acids taste sour  and bases taste bitter. Both acids and bases change the color of an indicator .

33. A base produces hydroxide ions, represented by OH. The OH is usually at the end of the chemical formula. Acids produce hydrogen ions, generally written at the front of the chemical formula.

34. Adding a little bit of acid to a buffer will cause the pH of the solution to stay about the same, probably increase a little. Buffer solutions are meant to make the pH "buffer". To remember, DVDs used to buffer. It's the same thing as "lag" for phones.

35-40: I'm sorry, I have no answer.

41. Electrons orbit like the plants revolve around the sun. Electrons revolve around a nucleus. A bee hovering around a bee hive  is probably flying around it in circles.

42. The tendency of an element to react is closely related to the number of valence electrons in atoms of the element.  If the valency is 8, the electron shell is full. The element is stable, opposite to reactive -- this applies to all noble gases (group 8A on the periodic table). If the valency is 1 or 7, the element is very close to being stable but not, the "desire" is so great and makes the element very reactive.