SOAL KIMIA KELAS X

Sistem Periodik Unsur 

1.      Susunan Berkala unsur-unsur Mendeleyev disusun berdasarkan ....

a.     Sifat kimia unsur

b.      Susunan elektron unsur-unsur

c.       Kenaikan nomor atom

d.      Kenaikan nomor massa unsur-unsur

e.      Sifat logam dan non logam

Penyelesaian:

Mendeleev menyusun unsur-unsur tersebut berdasarkan kenaikan massa atomnya untuk membentuk sesuatu yang sangat mirip dengan tabel periodik modern yang kita kenal saat ini. Bahkan, Mendeleev dapat meramalkan sifat-sifat dari beberapa unsur yang belum ditemukan saat itu.

Jawaban: D

2.       Kelemahan pengelompokan unsur oleh Newlans adalah....

1. Unsur yang sifatnya sama lebih dari 3
2. Terlalu umum
3. Tersedia tempat yang kosong
4. Sulit dipelajari
5. Terdapat beberapa unsur yang tidak sesuai dengan oktaf.

Penyelesaian:

J. Newlands  mengelompokan unsur-unsur berdasarkan kenaikan massa atom relatif. Newlandsmengumumkan penemuanya yang di sebut hukum oktaf. Ia menyatakan bahwa sifat-sifat unsur berubah secara teratur.. Unsur pertama mirip dengan unsur kedelapan, unsur kedua mirip dengan unsur kesembilan, dan seterusnya.

 Kelemahan dari teori ini adalah dalam kenyataanya mesih di ketemukan beberapa oktaf yang isinya lebih dari delapan unsur. Dan penggolonganya ini tidak cocok untuk unsur yang massa atomnya sangat besar.

 Jawaban: E

3.       Nomor atom unsur-unsur P. Q, R dan S berturut-turut adalah 20, 19, 18 dan 12. Unsur-unsur yang terletak pada golongan yang sama adalah …

a.       P dan Q

b.      Q dan R

c.       R dan S

d.      P dan S

e.      Q dan S

Penyelesaian:

                               K          L           M        N         Golongan,Periode

₂₀P                         2          8          8          2          IIA, 4

₁₉Q                         2          8          8          1          IA, 4

₁₈R                         2          8          8                       VIIIA, 3

₁₂S                          2          8          2                       IIA, 3

Berdasarkan data tersebut, unsure-unsur yang terletak pada golongan yang sama adalah P dan S.

Jawaban: D

4.       Diketahui nomor atom unsur X =12 dan nomor atom unsur Y = 15. Manakah dari pernyataan berikut yang benar mengenai kedua unsur itu?

a.       Jari-jari atom unsur Y lebih besar daripada jari-jari atom unsur X

b.      energi ionisasi unsur X lebih besar daripada energi ionisasi unsur Y

c.       elektron valensi unsur X sama dengan elektron valensi unsur Y

d.      keelektronegatifan unsur X lebih kecil daripada keelektronegatifan unsur Y

e.      daya tarik elektron unsur X lebih besar daripada daya tarik elektron unsur Y

Penyelesaian:

Berdasarkan nomor atom tersebut unsur X berada di sebelah kiri dan unsur Y berada di sebelah kanan.

                                          X  Y

Jari-jari atom dari kiri ke kanan semakin kecil(A bukan jawaban)

Energi ionisasi unsur dari kiri ke kanan semain besar. Energi ionisasi adalah energy minimum yang diperlukan oleh suatu atom dalam bentuk gas untuk melepaskan elektron yang terikat paling lemah. Energi ionisasi dari kiri kenan semakin bertamabah karena, ajri-jari atom semakin pendek, sedangkan muatan intinya besar. Dengan bertambahnya muatan inti, daya tarik inti terhadap elektron makin kuat, akibatnya elektron makin sukar dilepaskan.(B bukan jawaban).

C dan E bukan merupakan jawaban karena Elektron valensi unsure X tidak sama dengan elektron valensi unsur Y, dan daa tarik unsur X lebih kecil daripada daya tarik elektron unsur Y.

Keelektronegativan unsur dari kiri ke kanan makin besar. Hal itu disebabkan dari kiri ke kanan muatan inti bertambah, sedangkan jari-jari atom makin kecil. Akibatnya, daya inti terhadap elektron makin besar . Jadi, keelektronegatifan unsur X lebih kecil daripada keelektronegatifan unsur Y.

Jawaban: D

5.       Unsur P dan Q mempunyai konfigurasi elektron sebagai berikut:

                                      P : 2  8  7                         Q : 2  8  1

      Manakah satu di antara pernyataan berikut yang benar tentang kedua unsur tersebut?

a.       unsur P dan Q terletak satu golongan dalam sistem periodik

b.      unsur P mempunyai jari-jari atom lebih besar daripada unsur Q

c.       unsur P mempunyai energi ionisasi lebih besar daripada unsur Q

d.      unsur P lebih mudah membentuk ion positif daripada unsur Q

e.      unsur P tergolong logam sedangkan unsur Q tergolong non logam

Penyelesaian:

Unsur P memiliki elektron valensi 7, berarti unsur P terletak dalam golongan VIIA periode 3.

Unsur Q memiliki elektron valensi 1, berarti unsur Q terletak dalam golongan IA, periode 3

(Pilihan jawaban A salah).

Unsur Q terletak disebelah kiri unsur P, sehingga unsur P mempunyai energy ionisasi lebih besar daripada unsur Q. (pilihan jawaban C benar).

Unsur Q lebih mudah membentuk ion positif daripada unsur P. (D salah)

Unsur Q mempunyai jari-jari atom lebih besar dari unsur P. (B salah).

Sifat suatu unsur bergantung pada distribusi elektronnya. Unsur-unsur yang elektron valensinya kecil (  3) bersifat logam. Sementara itu, unsur – unsure yang elektron valensinya besar ( 4) bersifat non logam. Jadi, unsure P bersifat non logam dan Q bersifat logam (pilihan E salah).

Jawaban: C

Inorganic Report

I. TOPIC: Sodium Metal Reactivity

II. PURPOSE: Differentiate the reactivity of sodium metal in two different medium.

III.BASIC THEORY: Alkali Metal The alkali metals are a group of chemical elements in the periodic table with very similar properties: they are all shiny, soft, silvery, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements,¬¬ excluding hydrogen (H), which is nominally a group 1 element¬¬ but not normally considered to be an alkali metal. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones. The alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). All alkali metals have their outermost electron in an s-orbital. The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterized homologous behaviour. All the discovered alkali metals occur in nature. Experiments have been conducted to attempt the synthesis of ununennium (Uue), which is likely to be the next member of the group, but they have all met with failure. However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of superheavy elements. The atoms do not have a strong attraction for the single valence electron, and so it is easily lost (small first ionization energy) to from a +1 ion. Because they readily donate electrons in this way, all the alkali metals are strong reducing agents. They are quite reactive, even reducing water. Weak attraction for the valence electron also results in weak metallic bonding, because it is attraction among nuclei and numerous valence electrons that holds metal atoms together. Weak metallic bonding results in low melting points, especially for the larger atoms toward the bottom of the group. Cs, for example, melts just above roomtemperature. Weak metallic bonding also accounts for the fact that all these metals are rather soft.

 IV. TOOLS AND MATERIALS
1. Beaker Glass 200 mL
2. Cutter
3. Measurement Glass 50 mL
4. Tissue sufficient
5. Pipettes
6. Thinner 25 mL
7. Sodium Metal Little beat
8. Aquadest 25 mL
9. PP indicator ±2 mL

V. PROCEDURES:
1.added 50 mL of distilled water into the beaker.
2.Added 3 drops of indicator glass PP and PP indicator shaken to spread throughout the water layer. 3.added 25 mL of paint or paint thinner to two-phase separation is clearly visible.
4.Sodium metal is cut with a knife or a cutter and then cleaned with a paper towel to remove as much as possible paraffin, and then immediately put into a beaker.
5.Observed what changes or reactions that occur such as discoloration, presence of gas or changing the temperature (can be estimated by touch the outside of the beaker) and recorded in observation sheet. 6.Allow the reaction to completion (until all the sodium metal depleted), and throw straight into the hole sink while the water flowed from the faucets.

 VII. DISCUSSION

my animation_2

my animation_1

My Inorganic Paper_Cesium

CHAPTER I

PRELIMINARY

1.1.  Background

The alkali metals are lithium (Li),sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).This group lies in the s-block of the periodic table as all alkali metals have their outermost electron in an s-orbital. The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterized homologous behavior.

The alkali metals, found in group 1 of the periodic table (formerly known as group IA), are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements. As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water

Small amounts of caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Chernobyl disaster. As of 2005, caesium-137 is the principal source of radiation in the zone of alienation around the Chernobyl nuclear power plant. Together with caesium-134, iodine-131, and strontium-90, caesium-137 was among the isotopes with greatest health impact distributed by the reactor explosion.

The mean contamination of caesium-137 in Germany following the Chernobyl disaster was 2000 to 4000 Bq/m2. This corresponds to a contamination of 1 mg/km2 of caesium-137, totaling about 500 grams deposited over all of Germany.Caesium-137 is unique in that it is totally anthropogenic. Unlike most other radioisotopes, caesium-137 is not produced from its non-radioactive isotope, but from uranium. It did not occur in nature before nuclear weapons testing began. By observing the characteristic gamma rays emitted by this isotope, it is possible to determine whether the contents of a given sealed container were made before or after the advent of atomic bomb explosions. This procedure has been used by researchers to check the authenticity of certain rare wines, most notably the purported “Jefferson bottles”.