Why when I add new collections just one shard gets the data? - MongoDB

I'm studying sharding with mongodb and I have the follow structure:

• 1 Mongod to my ConfigServer with just 1 member in ReplicaSet
• 2 Shards each with 2 members in ReplicaSet
• 1 Mongos

I have one database named erp and 3 collections, pessoas, produtos and contatos.

So I have add my collections using:

sh.shardCollection("erp.<collection>", { id: 1 }, true)

I begin with collection pessoas, this collection have 2000 documents and are distributed this way:

mongos> db.pessoas.getShardDistribution()

Shard rs1 at rs1/desenv1:27019,desenv1:27020
data : 57KiB docs : 1497 chunks : 36
estimated data per chunk : 1KiB
estimated docs per chunk : 41

Shard rs3 at rs3/desenv1:27022,desenv1:27023
data : 19KiB docs : 503 chunks : 36
estimated data per chunk : 541B
estimated docs per chunk : 13

Totals
 data : 77KiB docs : 2000 chunks : 72
 Shard rs1 contains 75.27% data, 74.85% docs in cluster, avg obj size on        shard : 39B
 Shard rs3 contains 24.72% data, 25.15% docs in cluster, avg obj size on shard : 38B"

After this I have add the collection produtos, and I gave to her 1001 registers, so why this collection are distributed this way:

mongos> db.produtos.getShardDistribution()

Shard rs1 at rs1/desenv1:27019,desenv1:27020
 data : 67KiB docs : 1001 chunks : 1
 estimated data per chunk : 67KiB
 estimated docs per chunk : 1001

Totals
 data : 67KiB docs : 1001 chunks : 1
 Shard rs1 contains 100% data, 100% docs in cluster, avg obj size on shard : 69B"

Questions:

• Why only replicaSet "rs1" are getting data? The same thing happen with the collection contatos, only replicaSet "rs1" gets the data and I can't distribute the data to the other shard.

• Why this happens and what I'm doing wrong?

• How do I distribute equally the data? For example with 2000 registers, 1000 registers in one shard and 1000 in the another shard.

If you guys need more information just tell me.

Thanks