use the following choices to answer #11 -20.

a. alkali metals b. alkalineearthmetals c. transition metals d. halogens e. noble gases

11. have 1 valence electron
12. includes fluorine, chlorine, bromine, and iodine
13. groups 3 - 12.
14. have7 valence electron
15. other than he, have 8 valence electrons
16. have 2 valence electrons
17. include silver, ag, gold, au, iron, fe, and copper, cu
18. include magnesium, mg, calcium, ca among others
19. cannot judge valence electrons by their group number(s)
20. sodium is classified as one of these

Alkali metals = have one valance electron

Alkaline earth metals = have two valance electrons

Transition metals = Group 3- 12.

Halogens = have seven valance electrons

Includes fluorine, chlorine, bromine, iodine, and iodine.

Noble gases = Other than He have 8 valance electrons.

Explanation:

Alkali metals = have one valance electron

Alkali metals are present in group one. All alkali metals have one valance electron.

Alkaline earth metals = have two valance electrons

Alkaline earth metals are present in group two. All alkaline earth metals have two valance electrons.

Transition metals = Group 3- 12.

Transition metals are present in middle of periodic table. Transition elements are present in group 3-12.

Halogens = have seven valance electrons

Halogens are present in group seventeen. All halogens have seven valance electrons. Halogens elements ,

Includes fluorine, chlorine, bromine, iodine, and iodine.

Noble gases = Other than He have 8 valance electrons.

Noble gases are present in group eighteen. All noble gases are inert.

pre-sliced bread is a relatively recent development in baking technology. previous to that, it was always sold in a bakery in daily-made contiguous loaves with no wrapping, and was moderately perishable, usually being used with a day or two (which is why every bakery had a discounted “day-old” bread table.) therefore, pre-sliced bread would grow stale quickly. the hard crust provided a protective layer, and once the exposed dry slice left from the previous cut was removed, the interior was still soft.

what keeps bread soft is the moisture retained in the crumb (the light spongy part that’s not crust). the reason the crust develops is the surface of the dough gets exposed to hot dry air during baking which browns the outer layer and seals it, preventing all the moisture from escaping the dough. longer exposure to air will also eventually cause your bread to lose flavor and become stale.

people were used to cutting slices as they needed them and storing bread in a specially-made wooden or metal breadbox or pail with a lid to preserve it longer, but the first automatically sliced commercial loaves were produced on july 6, 1928, in chillicothe, missouri, using a machine invented by otto rohwedder, an iowa-born, missouri-based jeweler.[1] pre-sliced bread would indeed dry out, were it not for another 20th century technology: the plastic bag. bread could now be pre-sliced, and if the enclosing bag remains sealed as much as possible, the bread will remain soft and fresh for longer than if sitting unwrapped on a shelf or enclosed in a bread box that is not air-tight. sealed packaging meant bread could also be sold on store shelves and eliminate frequent trips to a bakery.

sealing bread in a plastic bag had another effect: the moisture in the loaf will re-distribute into the crust and soften it, which is sometimes more pleasing in a sandwich - especially for children whose teeth might not yet be strong enough to tear through a hard crust. a homemade loaf of bread can be sealed in a bag overnight and the crust will become soft like store-bought sandwich bread.

these were novel changes in how bread was produced and sold, which led to the coining of the phrase “the greatest thing since sliced bread.”