PLEASE HELP ill be asking more questions for whoever wants to help THANK YOU:) A. In a chemical reactions, substances after the arrow are called .
C2H4 + O2 → CO2 + H2O
1 products
2 reactants
3 no answer text provided
4 chemicals
B. In this reaction: sodium + water -> sodium hydroxide + hydrogen gas
which substances are the reactants?
1 hydrogen gas
2 sodium hydroxide + hydrogen gas
3 sodium + water
4 sodium hydroxide
C. This is an example of what type of reaction?
Mg + Fe2O3 → Fe + 3 MgO
1 decomposition
2 double replacement
3 single replacement
4 synthesis
5 combustion
D. This is an example of what type of reaction?
Ca(OH)2 + Al2(SO4)3 → CaSO4 + Al(OH)3
1 synthesis
2 decomposition
3 double replacement
4 combustion
5 single replacement
E. This is an example of what type of reaction? PbSO4->PbSO3 + O2
1 single replacement
2 combustion
3 double replacement
4 synthesis
5 decomposition
F. This is an example of what type of reaction?
C2H4 + O2 → CO2 + H2O
1 single replacement
2 double replacement
3 synthesis
4 decomposition
5 combustion

Each reaction has its own characteristics which can be determined from the reactants and products

Every chemical reaction involves a compound consisting of reactants and products

Reactants are compounds that react and form new compounds called products

There are several forms of reactions that can occur, including single replacement, double replacement, synthesis, decomposition, etc.

A. substances after the arrow are called 1 products

The product compounds in this reaction are: CO₂ + H₂O

B. which substances are the reactants : sodium + water

and The product compounds : sodium hydroxide + hydrogen gas

Reaction

2Na(s) + 2H₂O → 2NaOH(aq) + H₂(g)

C. Mg + Fe₂O₃ → Fe + 3 MgO is an example of single replacement :one element replaces the other elements of a compound to produce new elements and compounds

D. Ca(OH)₂ + Al₂(SO₄)₃ → CaSO₄ + Al(OH)₃  is an example of double replacement : there is an ion exchange between two ion compounds in the reactant to form two new ion compounds in the product

E. PbSO₄->PbSO₃ + O₂ is an example of decomposition : One compound breaks down into 2 components

F.C₂H₄ + O₂ → CO₂ + H₂O is an example of combustion : when Oxygen combines with hydrocarbon

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa